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INDICATOR 



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Class _JCJ^7^ 
Book ti&fi 

Copyright N° 



COPYRIGHT DEPOSIT. 



THE STEAM ENGINE INDICATOR 
AND ITS APPLIANCES. 



Being a comprehensive treatise for the use of constructing, erecting 

and operating engineers, superintendents, master mechanics, 

and Students, describing in a clear and concise 

manner the practical application and use 



STEAM ENGINE INDICATOR, 

With many illustrations, rules, tables, and examples for obtaining 

the best results in the economical operation 

of all classes of 

Steam, Gas and Ammonia Engines, 

Together with original and correct information on the adjustment of 
Valves and Valve Motion, Computing Horse Power of Diagrams, 
and extended instructions for attaching the indicator, its 
correct use, management and care, derived from the au- 
thor's practical and professional experience, extend- 
ing over many years, in the construction and 
use of the steam engine indicator. 

FOURTH EDITION REVISED. 

WILLIAM HOUGHTALING. 



THE AMERICAN INDUSTRIAL PUBLISHING CO., Publishers, 

Bridgeport, Conn., U. S. A. 

1906. 



-x 



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A* 



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LIBRARY of CONGRESS 

Tw§ Copiis Rtctived 

SEP 26 1906 

n Ctpynem Entry 
CLASS ^ XXC.N,. 

CO#Y B. ' 



COPYRIGHT 1899 



WILLIAM HOUGHTALING. 



ALL INTEREST AND RIGHTS RESERVED. 






DEDICATION. 

To the young Engineers of America, who by thoughtful and 
careful study ; are seeking to make their opportunities and overcome 
obstacles in the care and management of the Steam Engine; this 
volume is respectfully inscribed by 

The Author. 



PREFACE. 

The preparation of this book has occupied most of the author's 
spare time for a number of years. Originally the matter was not 
intended for publication, but the manuscript has grown so large and 
complete, which consideration, combined with many repeated re- 
quests, has induced the writer to publish the matter in book form. 

Let every Engineer make his own Indicator book as he proceeds 
in his study and practice, and it will prove invaluable in after years. 
The present work has been compiled in this way, from data contin- 
ually obtained during the author's professional career, extending over 
a third of a century. 

The introduction of algebraical for mules have been avoided. 
These are readily found in the many valuable mechanical Pocket- 
Books. The writer has endeavored to discuss the principle and use of 
the Indicator in as plain common sense words as the subject and the 
English language will admit of. 

Special attention has been given to the requirements of the young 
progressive student in Steam Engineering. The preparation of the 
following chapters has been a work of pleasure to the author, and if 
they prove beneficial to his fellow- workmen, he will be amply repaid. 



oettkmts 



CHAPTER. 

Brief History of the Indicator, - I. 

Purpose of the Indicator, - II. 

Definition of Technical Terms, ----- III. 

Construction of the Steam Engine Indicator, - IV. 

Indicator Appliances, '----- = V. 

Indicator Appliances, Continued, - VI. 

Indicator Reducing Motion, - - VII. 

Drum Stop and Electrical Attachment, - VIII. 

Care and Use of Indicator, - IX. 

To Take Diagrams, ------- X. 

Indicator Diagrams, .-.._. XL 

Study of Diagrams, ------- XII. 

Lines and Points of the Diagrams, - XIII. 

Isothermal Curve, ------- XIV. 

Adiabatic Curve and Point of Cut-off, - XV. 

The Foot Pound and Measurement of Diagram, - - XVI. 

Expansion of Steam, ______ XVII. 

Hyperbolic Logarithms- ------ XVIII. 

Theory of Action of Steam Expansion in Cylinders, . . XIX 

Reading the Diagrams, _--___ XX. 

Different Methods of Computing Water Consumption, - XXI. 

Indicator Testing Device, ------ XXII. 

Planimeters, .----._ XXIII. 

Comparison Diagrams from Throttling and Cut-off Engines, XXIV. 

The Economy of Expansion, - XXV. 

The Point of Cut-off, ------ XXVI. 

Back Pressure and Compression, ----- XXVII. 

Combining the Diagrams from Compound Engines, - - XXVIII. 

Diagrams From Gas and Oil Engines and Ammonia Compressors, XXIX. 

Making Calorimeter Tests, - XXX. 

Miscellaneous Diagrams, - - - - - XXXI. 

Engine Economy, .---••. _ XXXII. 

Tables, .............. XXXIII. 



CHAPTER I. 



BRIEF HISTORY OF THE INDICATOR. 



The idea embodied in this important and instructive little 
instrument, was originated by the celebrated James Watts dur- 
ing the latter part of the last century, at a very early period 
in the history of the steam engine, and it has since then in its 
improved forms, materially contributed to the perfection and 
efficiency of our modern steam engines , not only by enabling 
the engineer to ascertain the exact values of the forces from 
which the power is derived, but also by pointing out the pre- 
cise periods, in relation to the different parts of the stroke, at 
which these elements of power come into action. The original 
machine of Watts, consisted simply of a cylinder, about six 
inches long and one inch in diameter, in which there was a 
closely fitted piston; and was attached to the engine cylinder 
by means of a suitable pipe, fitted with a valve to open or close 
communication between them. A long open coiled spring was 
used of which one end was fastened to the piston, and the 
other to the cover of the indicator cylinder; this spring resist- 
ed the pressure of the steam, in one direction, and also the 
pressure of the atmosphere in the other. 



12 Steam Engine htdicator 

A pointer was connected to the piston, and moved directly 
with it and served to locate the atmospheric line, or zero ; and 
all motion of the pointer was above or below that point. 
There was no paper drum ; the pointer merely indicating on a 
scale, the highest and lowest pressure in the engine cylinder, 
measured from the atmospheric line. An improvement on this 
instrument was made by adding a flat slide to which a sheet of 
paper was secured and giving it a coincident motion, on a re- 
duced scale, with the engine piston, by attaching a cord from 
it to the crosshead or some other moving part of the engine, 
and returning the same by means of a counterweight. The 
machine in this improved form, though crude in comparison 
and less compact in construction, was almost identical in prin- 
ciple of its operation, to the many different instruments now 
so extensively in use, and it enabled him to ascertain the exact 
mean effective steam pressure throughout the stroke, and also 
the proportion which the vacuum in the cylinder, at different 
parts of the stroke, bore to that in the condenser, in order to 
determine the dimensions of cylinder required for any given 
power, as also the relative proportion proper to be given to the 
steam and exhaust ports, of the slow speed engines of his ex- 
periments. 

Having attained the objects, he left for succeeding engin- 
eers to devise, improve, and put into such a compact and por- 
table form, as to be easily applicable to steam engines of every 
description ; to such an extent as we find the modern indicator 
of to-day. 

One of the first to improve on the instrument of Watts, 
and nearly one-half a century later, was Wm. Macnaught of 
Glasgow, who constructed an instrument represented at one- 
quarter actual size in elevation, Fig. i, and in plan, Fig. 2. 

Unlike the indicators of to-day, that have a parallel and 
multiplied movement of the pencil as compared with the pis- 
ton ; in this instrument the movement of both are coincident, 



And Its Appliances. 



13 



that is, whatever motion is imparted to the piston by the steam, 
the pencil moves precisely the same distance either way. As 
constructed in this way, the spiral spring op- 
posing the force of the steam against the pis- 
ton, is liable to disarrangement, and uneven- 
ness ; on account of the greater length of 
spring necessary to obtain cards of a conven- 
ient height for computation. 

Its consequent general adoption has led 
to many very important, and decided im- 
provements in the construction of the instru- 
ment, and very materially aided in elevating 
the standard of duty of steam engines, and 
also demonstrated the economy resulting from 
a liberal use of the expansive power of steam. 
From a glance at Figure 1 , it will be per- 
ceived that the Indicator is neither more nor 
less than a small single acting steam engine 
with the addition of a spiral spring on the op- 
posite side of the steam piston, to resist the 
force of the steam. 

The many treatises at the present day on 
the steam engine indicator, leaves little to be 
said in reference to the actual manipulation of 
the instrument in practice : and we now find 
almost all of the Stationary, Locomotive, 
Marine, and other engineers imbued with the necessity of un- 
derstanding the working of the indicator in all its details, not 
only in the interest of their employers, but particularly for 
their own personal benefit, in acquiring a knowledge of the 
intricate working of steam, or other operating forces, of their 
engines, in all their various details, and which becomes neces- 
sary to enable them to reach a place in the higher ranks of en- 
gineering science. 




Fig. 2. 



14 Steam Engine Indicator 

The principal parts of an indicator, of the most complete 
construction, consists of an outside cylinder, or body, inside of 
which is secured an inner or working cylinder ; with a nicely 
fitting piston, of exactly one-half of a square inch in area, 
equal to about .7978 of an inch in diameter, working therein. 

The piston is so closely fitted to the working cylinder of 
the indicator, that at the pressures of from two to three hun- 
dred pounds per square inch, there is but a very small amount 
of steam that can pass by or through it ; but all indicators are 
subject to a certain amount of leakage of the piston, and for 
which ample means are always provided for its escape ; in or- 
der to avoid any unnecessary back pressure on the side of the 
piston opposite the steam pressure. 

Where the indicator is to be used for obtaining cards, from 
pressures ranging from four to six hundred pounds per square 
inch, it is advisable to use a reduced size of working cylinder 
and piston ; the area of which, shall only be one-fourth of a 
square inch; equal to about .5641 of an inch in diameter, thus 
avoiding the use of indicator springs of a very high tension. 
The different sizes of the working cylinders, and their pistons, 
are made interchangeable in the indicator, so that either can 
be removed at any time, and the other substituted. 

One end of the piston rod is connected to the piston, by a 
ball connected joint, and the opposite end to some part of a 
pencil mechanism, for producing a so-called parallel, or straight 
line movement of the pencil, up and down, in reference to the 
paper drum. 

„ The parallel motion is another beautiful and ingenious in- 
vention of Watts, as he applied it to steam engines, for the 
purpose of guiding the piston rod, back and forth in a straight 
line ; and without the intervention of any guides, or other 
means, for the purpose; thereby eliminating friction to a great 
extent ; with smooth working, and providing a mechanism that 
has since been used in various modified forms, and adapted, to 



A nd Its Appliances. 1 5 

a certain extent, to different kinds of machinery where a motion 
of this principle is desired. 

The parallel motion, as applied to his engines, was consid- 
ered by Watts, notwithstanding his other inventions, to be the 
one which gave him the greatest satisfaction and pride, as it 
performed its mission with the best practical results ; even 
though not absolutely mathematically correct in some respects. 
In most of our modern indicators this principle of mechanism, 
for their pencil movement has been almost universally adopted 
in its various and possible modified forms, and constant efforts 
in this direction are being made, with a view of eliminating 
the slight inaccuracies that are known to exist in the original 
parallel motion ; particularly in the constant varying ratio of 
the movement, that exists between the piston and the extreme 
end of the system or the point at which the pencil is located. 

The parallel or straight line movement of the pencil is 
usually produced by a system of levers and links of definite 
lengths, and pivoted in such a manner that by any movement 
of the system, up or down, the end of the lever carrying the 
pencil is always expected to move in a straight line, and also 
in some exact ratio to the movement of the indicator piston. 






Steam Engine Indicator 



CHAPTER II 



PURPOSE OF THE INDICATOR. 



The Steam Engine Indicator is an instrument originally 
designed for recording the varying pressure of steam in an en- 
gine cylinder ; at any, and all points during the revolution of 
the engine, and has subsequently been applied under many, 
and various other circumstances, wherever the record, and 
measure of an irregular pressure has been desired. 

The production of this record is the result of two motions, 
and is traced by the indicator pencil upon paper that is secured 
to a light cylinder, called the paper drum. 

To this drum is imparted a rotary oscillating motion upon 
its axis, at right angles to the motion of the pencil ; such mo- 
tion being derived from the cross head, or any part of the en- 
gine having a movement coincident with it. • 

The motion of the pencil is produced by the varying pres- 
sures of steam acting against the indicator piston ; in opposi- 
tion to the strength of a spring of known tension. Conse- 
quently, an indicator properly attached too, and communicating 
with the interior of the cylinder of a steam engine in operation, 
and the drum given a motion (on a reduced scale) correspond- 
ing to that of the engine piston, will, (on bringing the pencil 
in contact with the paper upon the drum, during its oscilla- 
tion), trace the outline of an irregular figure upon the paper, 
which is usually known as, and called an Indicator Diagram, 



And Its Appliances. 



17 



an example of which is represented in Fig. 3, CD. E. F. B. B. 
and shows the varying pressure acting against one side only of 




Fig. 3. 
the piston, during a revolution of the engine; and such pres- 
sures can be properly located, and correctly measured. 

The upper line C. D. E. F. of the diagram represents the 
force of the steam impelling the piston during its forward 
stroke ; while the back pressure line B. B. shows its retardation 
on the return stroke ; the average height of each being meas- 
ured, (by the scale of the spring), from the atmospheric line 
A. A. 

The difference between their average height, represents 
the Mean Effective Pressure, usually designated the M. E. P. 
of the diagram. 

The atmospheric line A. A, is also drawn by the indicator 
but at a time when steam communication between it, and the 
engine cylinder is closed; and consequently subjecting both 
sides of the Indicator Piston to atmospheric pressure only. 



1 8 Steam Engine Indicator 

To show the pressure on the other side of the engine pis- 
ton, another diagram must be taken from- the opposite end of 
the cylinder. 

In most calculations of the diagrams, it becomes desirable 
to draw, by hand, additional lines, from and by which, the 
actual lines may be compared. 

First, the straight line V. V. is drawn to represent the ab- 
solute vacuum, or absence of all pressure. 

Second, the line V. O. represents the clearance volume, 
and is drawn at right angles, (or perpendicular), to the atmos- 
pheric line. 

Third, the line O. O. is drawn to show the full boiler 
pressure in order that it may be seen on the diagram how near 
that pressure has been realized. 

The different lines, and events of the stroke, as shown by 
the diagram during a revolution of the engine, and the name 
by which they are designated will be noted, and explained in 
a later chapter. 

Diagrams taken from different engines, and under vary- 
ing conditions, will present themselves in an almost endless 
variety of forms, depending entirely upon circumstances con- 
nected with the operation. 

The earlier forms of the instrument, (although the same 
in principle), were crudely constructed, the moving parts ex- 
ceedingly heavy ; inducing vibrations, sufficient to vitiate, and 
distort the diagrams ; also causing more or less tardiness at 
the different events of the stroke, such as admission of steam, 
point of cut-off, and also compression ; because of the heavy 
parts being unable to respond so promptly to change of pres- 
sure ; thereby making them unreliable, and imperfect in their 
action, to an extent depending upon the weight of the pencil 
mechanism, rapidity of rotative speed, and also suddenness of 
change of pressure ; and therefore preventing their being suc- 
cessfully adaptable, only to engines of very low rotative speeds. 



A nd Its Applia?ices. 1 9 

The prevalence of many high speed engines in use at the 
present time, renders the use of the old type of indicators al- 
most useless, and wholly unsuited for high speed, where any 
reliable results are expected, as many details which gave little 
trouble at low speed, seriously affect the results at the higher 
speeds. 

The present improved construction of some of the various 
modern indicators, in which perfection is attained as near as 
can be expected, consists principally in superior designs, sim- 
plified construction, a better adaptation of the pencil mechan- 
ism, also finer adjustment, convenience of manipulation, and 
especially extreme lightness of the moving parts, thereby 
practically eliminating the effects of inertia, and momentum of 
these parts. 

These qualities in any Indicator are absolutely indispensa- 
ble in order to secure accurate and reliable results from high 
speed engines. 

The information that may be derived from a careful and 
attentive application of the Indicator to engines of all descript- 
ions, is almost incalculable to the engineer ; because many 
facts are accurately determined by its use, that cannot be ob- 
tained in any other way, with any great degree of satisfaction 
or correctness ; consequently its use has enabled the engineer to 
discover many unforseen, and necessarily unknown defects ex- 
isting in the engine, that have formerly been veiled in mystery, 
and at the present time, its value is so universally recognized, 
and relied upon, that most manufacturers of high grade en- 
gines, make provision for its application ; and do not consider 
their engines complete until the valves have been correctly ad- 
justed by the use, and assistance of the indicator, and set in 
such manner, as that the maximum efficiency of the engine 
shall have been attained. • 



20 Steam Engine Indicator 



CHAPTER III. 



DEFINITIONS OF TECHNICAL TERMS. 



The many terms, generally used in connection with the 
study of steam engineering, are all measurable ; each with 
reference to some established unit, and by which they are clear- 
ly defined, and their correctness recognized. 

Some of these are indispensable to the engineer, a few of 
which are briefly described, and explained as follows : 

The Unit of Work is equal in amount to the power required 
to lift one pound, one foot high, and is called the Foot Pound. 

The Unit of Heat, or Thermal unit, is the quantity of heat 
necessary to raise the temperature of one pound of water, one 
degree, or from 39 to 40 Fah. 

Also, one unit of heat is equal to 772 foot pounds or units 
of work. 

The Sensible Heat of any body, as Air, Water, or Steam, is 
the heat that is sensible to our touch, and in extent is as shown, 
and measured by the thermometer. 

Latent Heat of steam is the quantity of heat, (expressed in 
heat units), required to vaporize water, that has previously 
been heated to a temperature equal to the resulting steam, of 
vaporization. 

Specific Heat is the quantity of heat measured in thermal 
units, necessary to raise one unit of weight of the substance, 
through one degree of temperature. 



And Its Appliances. 21 

Saturated, or Dry Steam, is steam confined under pressure 
in contact with, the water from which it is formed, and contains 
just sufficient heat to maintain the water in a state of steam, 
and will vary in pressure, and density corresponding to vary- 
ing temperatures. 

When saturated steam suffers any loss of heat, a condensa- 
tion of some of the steam also takes place. 

Superheated Steam is steam containing an excess of heat. 

If to saturated steam more heat be added, its temperature 
will increase, and the steam is said to be superheated, because 
its temperature will be greater than that corresponding to satur- 
ated steam of the same pressure. This excess may be parted 
with, without condensation. 

Horse Power (H. P.) is the standard used for measuring 
the power of a steam engine, and is equal to lifting 33,000 
pounds one foot high in one minute of time, or 550 pounds in 
one second, or any equivalent thereof in opposition to the force 
of gravity. 

Indicated Horse Power, (I. H. P.) is the horse power of an 
engine as computed from the Indicator Diagram. 

If the mean area of the piston in square inches be 
multiplied by the mean effective pressure in pounds per square 
inch exerted against it, and also by its speed in feet per min- 
ute ; this product on being divided by 33,000, will be the 
indicated horse power of the engine. 

Net Horse Power is the indicated horse power of an engine 
less the horse power which is consumed in overcoming its own 
friction. 

Boiler Pressure is the pressure above atmosphere, or the 
pressure as shown by a correct steam gauge. 

Initial Pressure is the pressure in the cylinder acting 
against the piston, at or near the commencement of the stroke 
of the engine. 

Absolute Pressure is the pressure of the steam calculated 
from absolute vacuum. 



22 Steam Engine Indicator 



& 



It is the pressure as shown by a steam gauge, with the 
pressure or weight of the atmosphere added thereto. 

Terminal Pressure is the pressure above the line of abso- 
lute vacuum that would exist in an engine cylinder, provided 
the release of the steam had not taken place until the end of 
the stroke had been reached. 

Usually the release happens earlier, and in such case its 
position may be located by continuing the expansion curve by 
hand from any point of release, to the end of the diagram. 

The terminal pressure must always be measured from the 
vacuum line ; consequently it is the absolute terminal pres- 
sure. 

Mean Effective Pressure (M. E. P.) is the average of all the 
varying pressures at different parts of the stroke, exerted 
against the engine piston to impel it forward ; less all the 
pressure that acts on the opposite side of the piston to retard 
its progress. 

Back Pressure Line, in a non-condensing engine, represents 
the loss that occurs, from the retardation of the escaping steam ; 
due to a'tmospheric or other pressure 

It is indicated on the diagram by its height above the at- 
mospheric line, and is expressed in pounds per square inch. 

On the diagram of a condensing engine it is indicated by 
its height above a line drawn by hand to represent the absolute 
or perfect vacuum. 

Total Back Pressure is represented on the diagram by its 
height above the line of Absolute Vacuum. 

Initial Expansion is the fall of pressure along the steam 
line; which often happens in an engine cylinder, between ini- 
tial pressure, and the point at cut-off. 

Compression is a result caused by the action of the piston 
in compressing into the clearance space, all steam remaining 
in the cylinder after the exhaust valve closes. 



And Its Appliances. 23 

Clearance is all of the space or waste room between the 
piston at the end of its stroke, and the face of the valve. 

Its volume or amonnt is usually expressed in its per cent- 
age of the piston displacement. 

Piston Displacement is the distance passed over by the 
piston in traversing a single stroke. 

Its volume is equal to the area of the piston in square 
inches, multiplied by the length of stroke, in inches, the pro- 
duct is the volume of displacement in cubic inches. 

Wire Drawing is a term sometimes applied to the action 
of steam, and arises in consequence of very restricted steam 
passages, also dilatory valve motion, thereby reducing more or 
less, the pressure in the engine cylinders, and usually consid- 
ered to be a loss in the matter of economy. 

Valve Lap is the excess of length of the valve at each 
end ; (when at the middle of its stroke) over the extreme outer 
edge of the steam ports ; and is designed to serve as a cut-off 
valve within certain limits. 

Valve Lead is the amount of opening of the steam port, 
(which is regulated by the valve) for the admission of steam 
to the cylinder, just as the piston arrives at the corresponding 
extreme end of the stroke ; the entering steam thereby serving 
as a cushion for the reciprocating parts of the engine. 

Water or Steam Consumption is the amount of steam ac- 
counted for by the indicator, per horse power per hour ; and is 
a measure of the economy of the engine. 



^>T 



« 



to 



2 4 



Steam Engine Indicator 



CHAPTER IV. 



CONSTRUCTION OF THE INDICATOR. 



The principal difference in the construction of the various 
indicators on the market to-day lies in the pencil movement 
mechanism. The main objects sought in the design of this 

mechanism are as follows : 
ist, the nearest possible 
approach to straight line 
vertical movement of pen- 
cil parallel to the axis of 
the steam cylinder. 2nd, 
constant ratio of move- 
ment, pencil to piston. 3rd, 
lightness of moving parts, 
thereby reducing the mo- 
mentum of these parts to a 
minimum. 4th, accessibil- 
ity of the parts and conven- 
ience in handling same to 
take diagrams. 
For our intent and purpose, it is not necessary to describe 
more than one of the various instruments in the market to-day, 
and we have in preference to all others, selected the weil known 
improved new style Tabor Indicator, as shown in Figs. 4, 5 and 
6 as being the instrument more nearly fulfilling all the con- 




Fig. 5. 



And Its Appliances. 



25 



ditions and requirements named ; and which are absolutely 
necessary for the production of the most accurate results in 
Indicator practice, including lightness of moving parts ; there- 
by reducing momentum ; and also for ease and convenience to 
the operator in handling the instrument while taking diagrams. 
In order that the particular advantages of this instru- 
ment may be thoroughly understood, it is necessary that a 

brief description of its construction, 
and arrangement of parts, should be 
given here. 

The principal and most impor- 
tant peculiarity of this instrument 
from all others, lies in the method 
employed to communicate a straight 
line motion to the pencil, and at the 
same time of producing an exactly 
equal ratio of movement between 
the piston of the Indicator and the 
pencil ; both of which are perfectly 
accomplished by means of a steel 
plate, through which there is a slot (as shown, full size, in Fig. 
7), of such contour, or shape, as to exactly counteract the ten- 
dency to a radial movement of the pencil bar ; this slotted plate 
is attached in an upright position on the swivel plate of the 
instrument, and upon which the whole pencil mechanism is 
self-contained. The swivel plate is in turn secured to the cyl- 
inder cover of the instrument ; said cover serving as a center, 
upon which the entire pencil movement can be revolved in 
either direction, until it comes in contact with the paper drum. 
In order to make this slot in the plate available for the pur- 
pose, a small stud is secured on the pencil bar, upon which 
there is mounted a hardened steel roller, fitted so as to travel 
in the slot from one extreme to the other ; and in doing this, 




Fig. 6. 



26 



Steam Engine Indicator 



the pencil is caused to move in a straight line up and down the 
paper drum, in an exact ratio, throughout any and all parts of 
the movement, of exactly five times the distance moved by the 
indicator piston. 

The radial slot in the plate is an irregular curve and devi- 
ates slightly from a true circle ; the irregularities existing in 
the curve, just compensating for the error that would occur in 
case a radial link were substituted, and corresponding in length 
to the average radius of the slot ; where one end of said link 
is pivoted to a stationary point and the other to some part of 
the pencil mechanism ; a method now employed 
in a number of the well known indicators at the 
present time, and the results are, that the lines 
made by the pencil, which are supposed to be 
straight, are not so, nor are the ratios of piston 
and pencil equal. 

A radial link, the end of which always 
moves in a true circle, is therefore not a success- 
ful substitute for accuracy, as compared with 
the irregular curve in the slot plate of the Tabor 
Indicator, as said slot which guides and con- 
trols every movement of the pencil being so 
formed as to give the most accurate results, in 
. Fig. 7. every position the pencil bar may assume. 

There is another plate of exactly the same outline, as the 
slot plate (but without slot) and secured coincident with it ; 
the roll stud in the pencil bar projecting far enough through 
it to make contact with said plate, and serves to receive any 
pressure that may occur when the pencil is brought in contact 
with the paper drum in the act of taking diagrams ; and it also 
prevents the torsional strain that would otherwise come on the 
center and back links, thereby reducing the friction from this 
cause to a minimum. 




And Its Appliances. 



27 



These plates are provided with a projecting part on their 
lower ends, which are drilled and tapped to provide for a screw 
passing through, to regulate the pressure of the pencil upon 
the paper drum, said screw coming in contact with a standard 
secured to the body of the instrument. A small upright pro- 
jection on the swivel plate, serves as a fulcrum for the lower 
end of the back link, the upper end being connected to one end 
of the pencil bar. 

The back and center links are made of a fine grade of steel 
as also the pencil bar, which is hardened and carefully drawn 
to a spring temper, highly polished and all given a blue finish. 
The piston rod is of steel and made hollow in order 
to reduce weight, its upper end is connected to the cen- 
ter link, and the lower is made solid and terminates in 
a ball ; this ball is provided with a universal cap and 
socket and to which, in turn, the indicator piston is 
attached by means of a thumb nut. 

The piston rod is formed of three pieces ; the body, 
shank and ball ; and upon the shank there is formed a 
collar as shown at A, Fig. 8, full size, a little larger in 
diameter than the body, and serves as a safety stop for 
the pencil movement, by coming in contact with the 
under side of the cylinder cover just before the pencil 
bar reaches its extreme height, thereby preventing any 
further movement of the piston rod, which would be 
Yig. 8. likely to result in injury to the pencil movement in case 
of breakage of a spring when in use, or by a mistake of using 
too light a spring for the steam pressure. 

The piston is made very light, of a hard bronze metal, 
truly turned, grooved on its periphery, to act as a water pack- 
ing, and lapped perfectly round and straight on its face to an 
exact size. 

On the projecting arm of the instrument is secured a steel 
center stud, extending to the top of the paper drum, and around 



28 Steam Engine Indicator 

which all moving parts of the drum mechanism oscillate. The 
spring case has a threaded hub and is permanently secured to 
the stud, and rests directly on the top surface of the arm and 
is secured thereto by a nut underneath. 

A flanged disc, or pulley, which carries the paper drum 
has a projecting hub on both top and bottom, which insures a 
long and accurately fitting bearing on the stud, working almost 
frictionless. 

There is a hook secured to the bottom hub, which engages 
one end of a plain flat spiral spring, while the other end of the 
spring connects to a similar hook in the spring case. A part 
formed on the disc, is made to come in contact with a stop 
secured to the projecting arm of the instrument and serves to 
always locate it in a positive position, when alone under the 
tension of the spring. 

The lower hub of the disc rests directly on the spring case, 
while the opposite hub is in contact with a knurled thumb nut, 
screwed and pinned to the central stud, just sufficient to give 
a slight amount of end motion to the disc. 

This thumb nut also serves as a convenient means of reg- 
ulating the tension of the spring, as by loosening the nut that 
secures the spring case to the arm of the instrument, said 
thumb nut can be turned in either direction until the desired 
tension is obtained, and then tightening the nut. 

The lower part of the disc is formed with a groove, wide 
enough to receive about two turns of the cord ; one end of the 
cord being made fast to, and encircling the groove, and the 
other attached to a pantograph, pendulous lever, or some sort 
of a reducing gear that has a movement generally derived from 
the motion of the engine crosshead, and which causes the disc 
to rotate in one direction ; the motion in the opposite direction 
is accomplished by the retraction of the spring connecting the 
disc with the spring case, and its oscillations are thereby made 
coincident with the movement of the engine piston. 



And Its Appliances. 



29 



The drum upon which the paper is placed in taking cards 
is a very light cylindrical tube, mounted on the disc, and moves 
in unison with it. It has a guide permanently secured on the 
inside, and which fits in corresponding recesses in the disc, in 
order to serve as a carrier, and also to locate it in its proper 
position in reference to the pencil bar, for either right or left 

hand indicators. The Vop is 
closed and fitted with a sleeve 
that provides a bearing in 
contact with the central stud, 
and which serves as a guide 
for it, and prevents any irreg- 
ular motion at that point. A 
clip is attached for securely 
holding the paper, one leg of 
which is made shorter than 
the other to facilitate the 
matter of adjusting the paper 
upon the drum. 

One end of a plate of 
suitable outline, is shown in 
full size Fig. 9, and called the 
cord guide-base, is secured to 
Fig. 9. the under side of the arm of 

the instrument by a nut for that purpose, and said plate can 
be turned in any desired position parallel to it. The other end 
supports the cord-guide, which consist of a small grooved pul- 
ley mounted on a pin within the periphery of a circular disc, 
both being encircled by a clamp having a threaded stem, which 
projects through the plate, and is secured thereto in any desired 
position by a small thumb-nut, and the combination of the 
adjustment enables the cord to be correctly guided around the 
pulley and on to the flanged disc from any direction. 




30 Steam Engine Indicator 

The cock tube is securely screwed in the body of the in- 
strument at the bottom, and the connection which secures the 
indicator to the cock is made with a single thread, and secures 
correct attachment at once without the annoyance of different 
trials, as is often necessary with connections made with two 
threads. 

The indicator cock has a stop, which limits its range in 
either direction to full open or closed, and also has holes pro- 
vided for the release of all steam that may remain between the 
indicator piston and cock, after operating. In taking cards 
where two indicators are being used, one on each end of the 
steam cylinder, the straight cocks shown in Fig. 14, Chapter 5, 
are all that are necessary for the production of cards from each 
on separate sheets but in the case of only one indicator being 
used there is considerable trouble and annoyance, as well as 
time lost to the operator, in changing the instrument from one 

end of the cylinder to the other. 
All this may be entirely obvi- 
ated by the use of the three-way 
cock shown in Fig. 10, this cock 
being interposed about midway 
of the steam cylinder in a line 
of pipe connecting the two 
straight cocks at the ends of the 
Fig. 10. cylinder. This three-way cock 

furnishes an easy and convenient means of taking cards from 
each end of the cylinder, and within a few seconds of each 
other ; also on the same sheet of paper ; and therefore admits 
at once of a ready comparison between the cards. At all other 
times than applying the indicator, the cocks near the cylinder 
should be kept closed. 




And Its Appliances. 



31 




Fig. 1 1 is a 
sectional view of 
the three-way 
cock represented 
in Fig. 10. 

A very sim- 
ple and efficient 
cord attachment 
is shown in Fig. 
Fig. 11. 12, providing a 

convenient and easy means of adjusting the length of the actu- 
ating cord between the reducing gear and the indicator, the 
hook that is fastened on the cord from indicator connecting in 
the hole at the end of the attachment. 

Up to a comparatively recent date all indica- 
tors have been designed so that the piston spring 
comes more or less in contact with steam and hot 
vapors. This increases the temperature of the 
spring and tends to expand same thereby tending 
to increase the height of the diagram more than 
warranted by the steam pressure alone. To over- 
come this tendency the springs for the ordinary or 
inside spring type of indicator are graduated and 
calibrated to give correct pencil movements when 
subjected to these higher temperatures. The in- 
crements of temperature are variable under dif- 
ferent working conditions, and, while the inside 
spring type of indicator as shown in Figs. 5 and 6 will give 
reasonably accurate results with properly calibrated springs, 
it is obvious that a better construction would be to so locate 
the spring as to have it practically free from all such disturb- 
ing influences. The Tabor indicator is now made of both the 
inside spring type as shown in Figs. 5 and 6 and of the outside 




Fig. 12. 



32 



Steam Engine Judicata 



spring type as shown in Fig. 13. An examination of this cut, 
together with Fig. 13A will show that the spring is mounted 




Fig. 13. 



above the top cylinder cap where the temperature is but very 
little higher than the surrounding air. This construction is 



And Its Appliances. 



33 



desirable for high pressure steam work and especially for gas 
engine work where the temperatures run very high tending to 
make the spring unreliable and to suffer deterioration in the 
inside type of indicator. It will also be noted that with this 
construction the spring can be much more easily 
changed and without handling any very hot 
parts. It is not necessary to disturb the pencil 
motion or allow the indicator to cool off in order 
to change springs. 

It will be noted from the above that springs 
for outside and inside types of indicator vary. 

The general con- 
struction of the 
spring is practi- 
cally the same for 
both designs of 
indicator. See 
Fig. 13B. Each 
spring consists of 
two distinct coils 
of wire balancing 
each other, and 
both mounted 
with brass screw- 
ed ends. 

The principal 
requisites for a 
reliable and cor- 
rect spring are, that the wire should be of an exact size, and 
coiled on a special arbor of such a size that will give the proper 
tension to the spring for the different denominations. They 
should be evenly hardened and temper drawn uniformly all 
over, and in finishing should be made perfectly straight and 
true, thereby reducing to a minimum all the chances of any 




Fig. 13 A. 



Spring- for Inside Spring for Outside 

Spring Style Spring Style 

Indicator. Indicator. 

Fig. 13B. 



34 Steam Engine Indicator 

side strain or buckling of the spring, which always tends to 
force the indicator piston against one side of the cylinder, 
thereby creating a friction on the piston that will surely cause 
all results from it to be unreliable. The springs of the Tabor 
Indicator are made of different lengths, according to the denom- 
ination of the spring, the low pressure or light ones being the 
shorter, and from these continue to increase in length until 
the highest pressures have been reached. The principal object 
in making the springs of different lengths is that each may 
cause the pencil to mark the atmospheric line on the paper 
drum in an exact position in reference to itself, so as to have 
an ample range of movement of the pencil either above or be- 
low the line for both pressure and vacuum. This variation in 
the length of the spring obviates the annoyance and necessity 
of adjusting the length of the pencil connection to locate the 
position of the atmospheric line in cases where all springs are 
of the same length, as in some makes of indicators. 






And Its Appliances, 35 



CHAPTER V. 



INDICATOR APPLIANCES. 



It has been found advisable, in order to obtain the best 
results in indicator practice, to so construct the instrument 
that the piston shall have only a small amount of motion, and 
that the movement of the pencil shall bear a certain exact ratio 
to the movement of the piston. 

This ratio varies in different indicators ; in some, the pencil 
has four times, while others have five or six times the piston 
movement. 

This difference in ratio, as a general thing being a matter 
of selection, or convenience, of the makers in the designing of 
their indicators. 

One of the principal reasons for having the piston move 
but a short distance as compared with the pencil movement, is 
that a greater part of the friction between the piston and cylin- 
der, due to a long and rapid movement, is eliminated ; and 
consequently the results obtained from a short movement of 
the piston are much more accurate. 

By this it is not to be inferred that the shorter the piston 
movement the greater the accuracy ; as there are circumstances 
connected with the matter that prevent the realization of any 
theoretical conclusions, in reference to it ; because the ratio 
between the piston might be made so great that the slightest 
loss motion in the piston connections would be so multiplied 
at the pencil as to vitiate all efforts to obtain correct results. 



36 Steam Engine Indicator 

On the other hand, by making the ratio too small would 
tend toward the original principle ; where the piston and pencil 
had equal movement ; therefore, the best compromise between 
the two extremes becomes desirable, and an experience with 
different proportions seems to indicate that a pencil movement 
of five times that of the piston, is best adapted to average the 
imperfections that become involved in either a greater or less 
ratio. 

An important requisite, however, in this respect is, that 
whatever this ratio may be, is that the pencil shall move ex- 
actly that many times the distance moved by the piston 
throughout its entire range. This result has been perfectly 
accomplished in the Tabor Indicator through its specially de- 
signed pencil mechanism, which causes the pencil to move at 
any and every part of its travel of exactly five times the dis- 
tance moved by the piston, and this in connection with the 
straight line movement of the pencil, as well as the lightness 
of the moving parts and absence of friction always insures the 
accuracy of the diagram. 

Preparatory to taking indicator diagrams, it is well to see 
that the piping that connects the engine cylinder with the 
indicator has been properly done, and in the most convenient 
position to enable the operations to be performed successfully 
and with the least amount of anxiety and trouble to the opera- 
tor. The location of the indicator will, of course, depend 
somewhat upon the construction of the engine to which it may 
be applied, but the principal of its operation will always be the 
same in whatever position it may be placed. 

In the indicator piping on the .side of horizontal engine 
cylinders, care should be taken that the holes for the pipe are 
drilled outside of the point reached by the extreme travel of 
the engine piston at each end of the cylinder. This precaution 
is taken to insure that the piston does not close, or even partly 
close, communication between the inside of the steam cylinder 



And Its Appliances. 



37 



and indicator piston ; which would result in showing, in many- 
cases, a late initial pressure on the card, and otherwise cause 
it, to a certain extent, to be erroneous. It is also important, 
in all styles of engines, that these holes should be located as 
far from the steam ports of the engine as convenient, as there 
are instances in which a close proximity to said ports has to 
some extent influenced the pencil from indicating correctly, 
from the beginning of the stroke to the point of cut off ; this 
being due to the rapid inflowing of the steam through the ports 
and past the end of the pipe that communicates with the piston 
of the indicator ; thereby causing it to indicate a lower pressure 
than actually exists in the steam cylinder. 

The pipes, preferably of brass, should be as direct as pos- 
sible and without any unnecessary bends, and in cases where 

the regular straight indicator cock, shown 
in Fig. 14, is used at the centre, it is ad- 
visable to use straight way valves at the 
ends of the cylinder. 

There should be no appreciable dif- 
ference in the mean effective pressure, 
shown by the cards (under the same con- 
ditions), whether the indicator is located 
at the end or centre of the cylinder, that 
would be due to any difference in the 
length of pipe, within the limit of the 
length of the cylinder. A close com- 
parison of the card from the centre would 
only reveal a slight increase in the water consumption per 
horse-power over one taken at the end, and which is entirely 
due to the added clearance to the cylinder which would ensue 
from the greater length of pipe in use when the indicator is 
placed at the centre. 

The next matter of importance is in the selection of the 
best means of giving the paper drum an exact motion coincident 




Fig. 14. 



38 Steam Engine Indicator 

with the motion of the engine piston and cross head, on a suf- 
ficiently reduced scale, that will come within the limits of its 
motion; this distance being limited by the stop formed on the 
disc (that carries the drum) for that purpose. This entire dis- 
tance is never utilized in practice, as there must always be a 
certain amount of allowance at each end of its motion, to guard 
against any accident that might occur by corning in contact 
with the stop. 

There are various devices for the purpose of giving motion 
to the paper drum ; an example of the most usual ones being 
shown here in the illustrations, some of which are theoretically 
correct, while others are only an approximation. The length 
of the card to be taken, as well as its height, depends some- 
what upon the speed or number of revolutions the engine may 
be running per minute. 

In the slow speeds a long and high card may be taken, 
whereas in the higher speeds a short and low diagram is 
necessary, in order to avoid as much as possible the effects of 
inertia of the paper drum, and also of the pencil movement. 
With the new style Tabor Indicator, diagrams can be taken five 
inches long and two and a half inches in height if desirable, 
but with the ordinary speeds up to 100, and from that to 200 
•revolutions per minute, a length of card of 4 inches in the first 
instance, and 3^ in. the latter, will show well proportioned 
diagrams. As a guide in this matter it is recommended that 
with speeds up to 300 revolutions per minute the length of the 
card may be 3^ inches; of 400, 3 inches; of 500, 2^/ 2 inches; 
and of 600, about 2 inches long, which will insure reliable re- 
sults. The piston spring should also be of a higher tension 
(that is, a stronger spring), because, as the speed is increased, 
it becomes advisable to decrease the height of the diagram in 
about the same proportion as the length is shortened. 

Diagrams taken in these proportions seldom require any 
change of tension of the drum spring between the highest and 



A nd Its Appliances. 



39 



lowest speeds. The lazy tongs shown at about y& actual size 
in Fig. 1 5 is one of the appliances frequently used to obtain the 
necessary coincident motion (on a reduced scale) between the 
paper drum and cross head, and which it accomplishes in an 

accurate and satisfactory 
manner, provided the 
device is well made and 
free from all lost motion 
in its many pivoted con- 
nections. It is usually 
pivoted at the end (B) 
by a stud and winged 
thumb-nut to a block of 
wood, or an angle iron, 
secured to the floor of 
the engine room or in 
some other convenient 
position, while the end 
(A) is fitted in a suitable 
piece secured to the 
cross-head of the engine. 
The actuating cord from the indicator is attached to the cord 
pin (E) on the cross bar (C D) ; said cross bar may be moved in 
different positions with relation to the centre (B), by changing 
the screws C and D, which hold it in place, but the cord pin 
(E)must always be placed in a line with the centres (A) and (B). 
The position of the cross bar C D, in relation to B, deter- 
mines the length of travel of the cord pin E, and consequently 
the length of the diagram. No special care is necessary to 
locate the position of B, in reference to the cross-head of the 
engine, so long as the device works perfectly free throughout 
its range. One of the principal advantages of the Lazy Tongs 
over some of the other forms lies in its adaptability to the 
various different conditions so often found in indicator practice. 




Fig. 15. 



4-0 



Steam Engine Indicator 



Fig. 1 6 represents one way of attaching it to an engine, 
when the indicators are placed on the side of the cylinder. In 
this case it is worked in a horizontal (or flat) position, one end 
is supported by a standard secured to the floor, and of sufficient 




Fig. 16. 
height to just bring the cord pin (E) on a level with the cord 
guide on the indicator ; consequently, in this case, the cord will 
run direct from the cord pin to the indicator. 

They may also be used in a vertical position with equally 
good results, where the end B is attached to a low block or 
bracket secured to the floor, and directly below the engine 
cross-head. In this position it becomes necessary (in order to 
insure coincidence between the cross-head and paper drum) to 
use a small carrying pulley, over which the cord must pass from 
the cord pin, E, and thence to the indicator. Said pulley may 
be mounted on an additional suitable block that will admit of 
its being placed exactly on a level with, and a short distance 
from the cord pin, E. 

There are various other ways of applying the Lazy Tongs, 
as circumstances may require, which will suggest themselves 
to the engineer, all depending entirely upon occurring condi- 
tions. 

Proportion of Lazy Tongs. In order to enable the engineer 
wishing to construct an accurate device similar to that shown 
in the illustration, the following data will need to be carefully 
observed to insure an accurate motion. 



/iud Its Appliances. 41 

The instrument is constructed principally of strips of 
thoroughly seasoned cherry wood about one and -\ne-eighth 
(i}i) inches wide, by three-eighths (}i) inch in thickness. 

The distance apart of the outer holes in the long strips is 
sixteen (16) inches, while the length of the short strips con- 
necting their ends are only one-half of that, or eight (8) inches 
between similar holes. 

In the cross- bar C. D. there are eleven additional holes, 
one-half ()4) of an inch apart, placed equidistant from each 
end, and are threaded to admit of the cord pin E, being screwed 
therein in its various positions on the cross bar. 

In one of each of the long and short strips are also eleven 
threaded holes, one-half { l / 2 ) inch apart and exact duplicates of 
those in the cross bar CD. and to which the cross bar is secured 
by screws in any desired position, as shown in the illustration. 

The pivoted joints are constructed of brass tubing about 
five-sixteenths (5- 16) inch outside diameter, by three-sixteenths 
(3-16) inch inside, and of sufficient length to go through the 
joints and be riveted over iron washers on each end. 

This construction also provides a means of tightening the 
pivots in case they become loose from wear, by a further rivet- 
ing over of the tubing. 

There is also placed upon the pivot between each joint, 
two thin brass separating washers to prevent the strips of wood 
coming in contact with each other while in operation ; thereby 
obviating the friction that would otherwise take place. 

The studs A and B are shown one-half size in Fig. 17 and 
are made of round steel, seven-sixteenths (7-16) of an inch in 
diameter, and three and one-half (s}4) inches long. In the 
middle of their length is secured a collar three-quarters inch in 
diameter and one-quarter of an inch in thickness. Each of 
these studs on one side of the collar are made with nut and 
washer, and serve as pivots to connect the ends of the device. 



42 



Steam Engine Indicator 




The opposite end of stud A is made either straight or 
tapering as occasion requires, to connect with the cross-head ; 
while the opposite end of stud B, is threaded, and provided 
with winged nut, for the purpose of attaching to the fulcrum, 

or to whatever the device may be 
suspended ; as before mentioned. 

In order that the cross bar may 
not come in contact with the nut and 
washer of the stud B, when the de- 
vice is closed, the bar is elevated by 
means of two wooden washers, one 
Fig. 17. at each end, made of the same mate- 

rial as the strips, and the screws for securing the same are of 
sufficient length to reach through both, and screw into the 
drilled strips underneath. 

It is exceedingly important that all corresponding holes in 
the strips be layed out and drilled with extreme accuracy, and 
also the pivots made a close fit therein, to insure its perfect 
working at all points, from its closure to the full extension. 

In this construction of the Lazy Tongs, the location of the 
holes, their distance between centres, and the position of the 
cross bar in relation to the stud B,' determines the ratio (that 
occurs in each case) in the amount of motion of the cord pin E, 
as compared with the amount of motion of the stud A. 

The holes being one-half inch apart, a change of the cross 
bar from one hole to the next, results in a change of motion of 
the cord pin E, of one-forty-eighth. 

For instance ; If the cross bar be secured in the holes that 
will bring it nearest to the stud B, and if the cord pin E, there 
be placed in the hole that comes in line between the studs A 
and B, the reduction of motion of the cord pin will be three- 
forty-eighths, or one-sixteenth of that- of the stud A; in the 
second hole the reduction is four-forty-eighths, or one-twelfth ; 
in the third hole, it is five-forty-eighths ; in the fourth hole 



And Its Appliances. 43 

it is six-forty-eighths, or one-eighth and so on, to the farthest 
holes from B, where the motion of the cord pin becomes thir- 
teen-forty-eighths of that of the stud A. 

From this it will be seen that each position of the cross bar 
has its own ratio of movement between the cord pin, and stud 
A, as above, whatever the length of stroke of the engine may 
be. 

In every position of the cross bar C. D. (if made according 
to directions), there is always one of its holes on an exact line 
between the centres of the studs A and B, and into which the 
cord-pin E, must always be placed in order that it may move in 
an exact straight line parallel to the motion of the stud A. 



# t % 

W/ i \W 



44 



Steav i Engine Indicator 



CHAPTER VI. 



INDICATOR APPLIANCES CONTINUED. 



An accurate and simple form of pantagraph is shown in 
Fig. 1 8, in which the end, A, is connected with the engine 

cross-head by means of a 
pin or other suitable con- 
nection ; while the end, B, 
is pivoted to a bracket, C ; 
said bracket also serving 
as a support for the guide 
pulley, E, and upon which 
it may be adjusted at a 
level to coincide with the 
cord pin, D. 

The length of travel of 
the cord pin depends en- 
tirely upon the distance 
the cross-bar, F, may be 
placed in relation to the fulcrum, B. There is a slot in this 
cross bar which admits of an adjustment, and the securing of 
the cord pin, D, in any required position within the length of 
the slot ; and in whatever position the cross bar may be placed, 
the cord pin must always be moved and secured by means of 
the thumb nut, on a line between the points A and B in order 
to insure an exact straight movement of the pin, D, and paral- 
lel with the engine cross-head. 




A?id Its Appliances. 



45 



This instrument, like the Lazy Tongs, may be used in 
either a horizontal or vertical position ; it has a less number of 
pivoted connections and accomplishes equal accuracy ; but has 
not quite the same range of application under all circumstances. 
In all cases and with either instrument, where they are placed 
in a position requiring the use of a carrying pulley, care must 
be taken that said pulley, E, be located a short distance from 
the instrument, and in such position that the actuating cord 
will move parallel with A, from the cord pin, D, to the pulley, 
E, and thence in any desired direction to the Indicator. 




Fig. 19. 

Fig. 19 represents the pantagraph in its application to an 
engine cylinder, where the indicators are placed upon the side 
of the cylinder. In this case blocks of wood or iron is shown, 
secured to the floor, to serve as supports for the instrument, as 
well as the carrying pulleys ; this arrangement answers the 
purpose, but the bracket, C, in Fig. 18, is much more me- 
chanical. 

A simple method of obtaining the drum motion, and very 
frequently used by engineers (in the absence of a more accurate 
device), is the pendulous lever, A B, shown in Fig. 20, which 
consists of a strip of wood, about 4 inches wide, by ^ inches 
thick, and suspended from a bracket, G, which is secured to 
the ceiling or any overhead framing ; the lever being of suffi- 
cient length from its point of suspension, so that its lower end, 



4 6 



Steam Engine Indicator 



1 



^V~P 



A, may connect to one end of the connecting bar, C, while the 
opposite end "of said bar is attached to the engine cross-head, 

D. The length of the lever, A B, 
" should be such that the end, A, 
should be as far below the line of 
movement of the cross-head, when 
on its center of travel, as it will 
be above the line at its extreme 
end of stroke. 

The cord pin, E, (to which one 
end of the indicator cord is at- 
tached), is located at such a dis- 
tance from the point of suspen- 




sion, B, as will rotate the 



paper 



drum, an amount that will give the 
Fig. 20. desired length of the diagram. 

In this device it is necessary to pass the cord from the pin, E, 
over the guide pulley, F, and thence 
to the indicator. In connecting the 
device, it is important that the cross- 
head, D, should be at its center of 
travel, when the lever, A B, is in a 
vertical position. 

This reducing motion may be easily 
and cheaply constructed and set up by 
any engineer, and will be found a con- 
venient means of giving motion to the 
paper drum ; but although not mathe- 
matically correct, will give fair results. 

Fig. 21 shows another device, the 
same in principle, but instead of the 
cord pin there is substituted a segment 
of a circle, having its center at B, and with a radius necessary 
to give the paper drum the desired amount of motion. 




And Its Appliances. 



47 



In place of the connection, C, as in Fig. 20, the lower end 
of the lever at A is slotted and is worked by a stud, secured to 
the engine cross-head, D. Whenever this device can be placed 
in a direct line with the indicator, the guide pulley can be dis- 
pensed with, and the cord encircling the segment may be run 
from it directly to the indicator. 

As the relative length of the lever in this arrangement is 
constantly changing throughout its stroke, it is therefore as to 
the matter of inaccuracy about equal to Fig. 20. 

The plan of suspended lever, shown in Fig. 22, is an im- 
provement on the previous ones shown, and was proposed by 



1 



A 



gh— ■ 



« 



Mr. Frank Richards in 
an article published in 
the American Machinist 
several years ago, in 
which he gives a number 
^ of modifications of the 
same principle, whereby 
perfect theoretical ac- 
curacy is attained. It 
consists of an ordinary 
suspended lever, with 
the lower end, A, slotted 
and driven by a pin se- 
cured to the engine cross- 
head ; the end, B, being 
pivoted to the bracket, 



-A 

""Fig. 22. 

G, which may be secured to the ceiling or some suitable frame 
work (or it may be used in a horizontal position if desired) ; 
the other element of the lever at C also being slotted, and giv- 
ing motion to a sliding bar, F, by means of a pin fastened to 
said bar, and working freely in the slot in the lever. The bar, 

F, slides in hangers secured in the same manner as the bracket, 

G, and in a line parallel to the line of the cross-head. The 



48 Steam Engine Indicator 

cord, attached to trie sliding bar, passing in a line over a suita- 
ble guide pulley and thence to the indicator. By this arrange- 
ment the relative length of the elements of the lever, A B, al- 
ways remains the same, and consequently insures coincidence 
and accuracy of the drum movement, throughout its entire 
range. 

The various different modifications of this principle, to at- 
tain accuracy of the drum motion, depends upon the use of the 
sliding bar, F, in each instance, and it is evident, as well as 
readily seen, that it makes no difference (so far as accuracy is 
concerned), whether the lever, A B, is slotted, or instead of the 
slots, we substitute two permanent pins in the lever, and have 
each pin work in slots formed in both sliding bar, F, and in a 
suitable slotted piece secured to the engine cross-head. 

Figs. 20, 21, and 22 show the position of the lever, A B, 
when engine cross-head is at the center of its stroke. In order 
to determine the proper distance (of the point on the lever to 
which the cord is attached), from the fulcrum, B, to take any 
desired length of card, it is necessary first to divide the stroke 
of the engine cross-head, in inches, by the desired length of 
the card required ; then divide the total length from center to 
center of the lever, A B, by that quotient, which will give the 
distance of the point in inches from the fulcrum, B, to the pin, 
E, or where the cord must be attached. For example, sup- 
pose the stroke of the cross-head to be 24 inches, the length of 
the lever, A B, between centres to be 48 inches ; and we desire 
to produce an indicator card 4 inches long ; then 24 inches di- 
vided by 4 inches, the length of the desired card, is equal to 6, 
and by dividing the length of the lever, A B, which is 48 
inches by 6, gives us 8 inches, which is the proper distance 
from the fulcrum, B, to a point on the lever to which the cord 
must be attached to produce a card 4 inches in length. 

A slight discrepancy will sometimes appear in the length 
of cards, computed from any rules, owing to incorrect meas- 
urements, stretching of the cord, inertia of the paper drum, &c. 



And Its Appliances. 



49 



3 



Fig. 23 shows another modification of the lever and slid- 
ing bar, F, in which the 
slots in the lever have been 
dispensed with, the lever 
beinsf attached to the cross- 



(jQ^S^head and bar F by means 
of the connections A H 
and C E. An important 
matter in this construction 
is that the lengths of the 
two connecting links must 
bear the same ratio to each 
other, as the ratio between 
the two elements of the 
lever, A B and B C ; there- 




Fig. 23. 

fore AB:BC::AH:CE. The pins on the cross-head and the 

sliding bar must be so located that lines drawn through the 

centres of the connections A H and C E, will be parallel with 

each other in any position 

the lever may assume. In "* 

the arrangement shown in 

Fig. 24 the fulcrum of the 

lever is at the pin, C, of 

the sliding bar, F, while 

the ends are each made in 

the form of a fork, the end, 

A, being moved by and 
sliding upon a pin secured 
to the cross-head, the end, 

B, moving on a pin fasten- 
ed to the bracket, G. In Figs. 23 and 24 the cross-head is 
represented at the extreme end of the stroke. 




Fig. 24. 



5o 



Steam Engine Indicator 



These are modifications of Fig. 22, but without claiming 
any particular advantage for one over the other. In all cases 
where this principle is accurately applied, it will be found that 
the elements of the lever, A B, are always in a line at a right 
angle to the line of movement of the engine cross-head, at the 
time the cross-head is at the centre of its travel. 

The sliding bar principle may also be well adapted to en- 
gines where the end of the engine -shaft is accessible. By in- 
serting a stud, A, in the end of the shaft, as shown in Fig. 25, 
at a proper distance from the centre, C, to give the desired 
length of card, and connecting it to a sliding bar, F, by means 

of a short connection, 



A B, will insure a per- 
fect coincident motion 
of the engine cross-head 
on a reduced scale. The 





Fig. 25. 

bar may be extended to any desired length to secure conven- 
ience in connecting Avith the indicator. A necessary requisite, 
to insure correctness by this arrangement, is that the length of 
the connection, A B, relative to the distance of the end, A, 
from the centre, C, must bear the same proportion that the 
main crank of the engine bears to its own connecting rod. It 
is not necessary in this case that the slide move parallel with 
the movement of the cross-head, as it may be moved in any desir- 
ed direction, but great care must be taken that stud A be placed 
in such position on the shaft that the sliding bar, F, will be on 
its extreme throw at the same exact time that the engine crank 
is at its extreme movement, and both at the same end of the 
stroke. Where the end of the shaft is not accessable, the same 
results may be accomplished by means of an eccentric placed 
in a convenient position on the shaft. 

A reducing arrangement, that gives good results at high 
speeds, is a plain lever swinging on a pin above (or it may be 
below) the cross-head, having a pin in the end which slides up 



A nd its Appliances. 



51 



and down in a slotted piece of metal fastened to the cross-head 
as shown in Fig. 26. This method gives a fairly accurate 
motion. A segment of a grooved pulley is fastened to the 




Fig. 26. 
upper end of the lever, and from this the cord extends to the 
indicator. 

The whole device should be made of wood as light as pos- 
sible, (consistent with strength), in order to reduce the inertia 
to a minimum. A heavy reducing gear on a high speed engine 
will wear very quickly and create inaccuracies in the diagram. 

When indicating High Speed Engines or Locomotives, the 
driving cord for hooking on the indicator should be continued 
beyond the loop, and fastened to a spring or an elastic band 
attached to the carrier pulley of the indicator. 

This band or spring is intended to always keep a tension 
on the driving cord, whether the indicator is in operation or 
not, and prevents entanglement and breakage of cord when 
the indicator is unhooked. 

The cut in Fig. 27 shows the arrangement as described, 
and which operates in a perfect satisfactory manner, as dia- 
grams can be taken with as little difficulty at high speeds, as 
on slow speed engines. 



52 



Steam Engine Indicator 



The hook, A, on the indicator cord connects into the loop, 
B, on the driving cord when the indicator drum is in operation ; 




Drill 

Fig. 27. 
the loop, B, is made long enough to be held with the hand 
when hooking on the indicator. 

To disconnect, merely catch the hook and hold it station- 
ary for a second, and the loop will come off. The rubber band 
then takes the motion and keeps the cord taut. 

Whatever arrangement is employed, it is desirable to avoid 
the use of long stretches of cord on account of its sagging and 
stretching. Small wire may be used to good advantage on 
vertical lengths except where the line passes over pulleys. 

Whatever the style of reducing motion that may be em- 
ployed for giving motion to the indicator drum, its accuracy 
can easily be tested, and ascertained in the following manner: 
Lay off a number of points on the cross-head guides, at say }i , 
%, }&, }4, yi in. etc., of the stroke. 

Connect the Indicator with the reducing motion in the 
same manner as for taking diagrams. When the cross-head 



And Its Appliances. 53 

is on either dead centre, bring the pencil in contact with the 
paper on the drum and make a short vertical line. 

In the same manner make other lines on the paper, as the 
cross-head is moved to each successive eighth point on the 
Qfuide. 

Then if the lines on the paper are exactly at eighths, the 
motion of the cross-head has been accurately reduced. 

These directions given for reducing motions are general ; 
some special cases require special modifications. 



t T % 



54 



Steam Engine Indicator 



CHAPTER VII. 



INDICATOR REDUCING MOTION. 



There are a number of devices tinder different names, all 
designed for the purpose of giving the necessary accurate mo- 
tion to the paper drum ; 
and each constructed on 
principles in which long 
swinging levers are dis- 
pensed with, the actuating 
cord from these devices 
being connected either 
directly to the engine cross- 
head, or to some moving 
part that has a motion in 
exact unison with it ; -while 
another and separate cord 
connects the device with 
the indicator. If, in the 
act of operating the indi- 
cator with any of these 
devices, it becomes desir- 
ous of stopping the mo- 
tion of the paper drum, it 
is necessary to disengage, 
or unhook, either one or the other of the cords that give it mo- 
tion ; a matter with some of them, requiring considerable 




Fig. 28. 



And Its Appliances. 



55 




Fig. 29. 



practice to accomplish with ease and assurance especially on 
engine having high rotative speed. This operation of unhook- 
ing is usually performed on the cord connecting the device 
with the Indicator. Some of these attachments are constructed 
so as to be attached to the indicator by means of a bracket, 

adapted to the particular 
indicator to which it is to 
be applied ; while others 
are so made, that may be 
secured away from the in- 
dicator, to some part of the 
cylinder or engine framing 
by means of set screws or 
bolts ; in many cases re- 
quiring considerable labor 
to secure them in a con- 
venient position. 
The particular Reducing Gear, of which we shall give a 
description in this article, is one that is constructed with and 
forms a complete part of the well known Tabor Indicator, 
as illustrated in Fig. 28. After securing the indicator 
in position on the pipe connecting with the engine cylinder, 
and attaching the end of the actuating cord to a stud 
screwed in the cross-head, the instrument may be used during 
the time of any experiment, without the necessity of connect- 
ing and disconnecting the actuating cord, in order to start or 
stop the motion of the per drum. 

The principal parts of this Reducing Gear consists of sup- 
porting base K, Fig. 29, with two short standards, B, and B 1 . 
The standard B 1 is fitted with a hardened steel center P, Fig. 
30, which serves as a pivot bearing for the end of the worm 
shaft R, Fig. 31, and which receives the entire thrust of the 
shaft R, thus reducing the friction from that factor to a mini- 

The base 



mum 



the other bearing being in the standard B. 



56 



Steam Engine Indicator 



Fig. 30. 





Fig. 31. 



K is connected direct to the Indicator, upon the projecting 
arm that supports the paper drum B, and the teeth of the 
worm shaft, R, engage directly with the teeth on the drum car- 
rier g, thereby 
making a posi- 
t i v e connec- 
tion therewith, 
and forming a 
part of the In- 
dicator, (see 
Fig.28). Tothe 
base K, is also 
connected the spring case D, Fig. 32, permanently secured 
thereto, by means of screws passing through holes as shown in 
the spring case, and corresponding with holes tapped into the 
standard B, (as shown) of base K, and so located thereon that 
its centre shall be common with the center of the worm shaft R. 

Upon the worm shaft R, is secured 
by means of a set screw, the collar A, 
through which freely slides the clutch 
pin I, one end of which is securely fas- 
tened to the thumb piece U, by which the 
pin is operated. The whole mechanism 
of that part is shown complete in Fig. 33. 
The flanged pulley O, Fig. 34, rotates Fig. 32. 

freely and independently forward and back on the worm shaft 
R. It has its outer hub formed in the shape of 
a double cam clutch, with steel pins X, X, in- 
serted to prevent wear upon their faces, while 
the opposite side has a hole in which the pin A, 
of the spring case cover S, Fig. 35 engages. 
One end of the actuating cord is attached to the 
pulley O, (a hole being shown in the figure for that purpose) 
while the other is secured either to the engine cross-head ; a 





Fig. 33. 



And Its Appliances, 



57 




Fig. 34. 



standard bolted to the same, or to any other part that has an 
exact similar movement, and should be connected from the 
pulley O, in a line parallel to the movement of the cross-head. 
The length of the actuating cord should be such, that when 
connected to the cross-head, at the commencement of the outward 
stroke of the engine, there should also be 
about six or seven turns of the cord encir- 
cling the pulley O, which will always in- 
sure the requisite amount of cord, and ob- 
viate -the liability of breaking. 

Enclosed in the spring case D, Fig. 32, 
(not shown in the illustration) is a small plain 
Spiral Spring ; one end of which is secured 
to the spring case by means of a slot F, shown in the figure, 
while the other end connects with the hook C of the spring 
case cover S, Fig 35. This spring operates to return the pul- 
ley O, back to its starting point, after it has been revolved in 
one direction, by the outward movement of the engine cross- 
head ; therefore as this pulley O, has an independent rotating 
forward and back motion on the worm shaft, R, the necessity 
of unhooking the cord in order to stop the motion of the paper 
drum B, after the diagram has been taken, will be entirely 
overcome, as explained further on. 

The paper drum B, is rotated forward 
by means of the pulley O, through the 
worm shaft R, engaging with the teeth of 
the gear g, on the drum carrier ; and in the 
opposite direction by the action of its own 
retracting spring. On the top of the drum B, is a knurled 
thumb-piece, with a projecting pin on its under side, for the 
purpose of engaging with a similar pin, secured in the top of 
the drum, and is to be used by the operator when in the act of 
starting the drum ; for the purpose of moving it slightly for- 
ward before the clutch pin I, is pushed in engagement with 




58 Steam Engine Indicator 

the cam hub of the pulley 0, thereby preventing the drum 
carrier from striking against its stop on the return motion. 

With this reducing gear the stopping of the drum motion 
becomes a very simple matter, and is accomplished by taking 
hold of the thumb piece U, and withdrawing the engagement 
between the clutch pin I and the clutch hub of the pulley O. 

The knurled thumb piece on the top of drum B, also fur- 
nishes another very convenient (and preferable) means of stop- 
ping the motion of the drum ; as by holding it so as to retard 
the motion of the drum on its return stroke, it will thereby 
cause the cam face of the pulley O, (which is constantly in mo- 
tion) to automatically force the clutch pin I out of contact with 
the clutch hub of the pulley O. The starting or stopping of 
the paper drum, at any time, will have no effect on the motion 
of the pulley O, which will continue to revolve independently 
while the engine is in motion. When desirous of starting the 
drum B, it will be necessary to again make the engagement be- 
tween the clutch pin I and the clutch hub of the pulley O, and 
which must be done by the combined means of the thumb 
piece U, and the thumb piece on top of drum B, as follows: 
The pulley O, being in constant motion ; with one hand take 
hold of the thumb piece on top of drum B,. and turn it in a 
direction from right to left, until it carries the drum and its 
carrier a short distance from its stop, (say about y^ inch). 
While holding the drum in this position, take hold of the 
thumb piece U, with the other hand and gently press it toward 
the clutch hub of the pulley O, and it will be found that when 
the engine cross-head arrives at its extreme inner stroke,, that 
the engagement between the clutch pin I and the clutch hub of 
pulley O will ahvays take place at that particular point, and 
with the least amount of difficulty in the operation. 

The thumb pieces are so constructed that they may be 
readily held in the hand while running; therefore no difficulty 
is experienced in throwing the clutch pin in or out of gear. In 



And Its Appliances. 5g 

preparing to use this Reducing Gear, the first and very im- 
portant matter for consideration is in the selection of the pul- 
ley O, which shall be of such size in relation to the stroke of 
the engine as will give the requisite length of the Indicator 
Diagram . 

A ready and mental means of ascertaining this, is by divid- 
ing the length of the stroke of engine (in inches), by twelve, 
which will give the diameter (in inches), of the pulley O, that 
is, the stroke of the engine being 12 inches will require the 
pulley O to be one inch in diameter ; a stroke of 1 8 inches, 1 y 2 
inch ; of 24 inches, 2 inch ; and of 36 inches a pulley of 3 
inches in diameter, &c. ; and it is also well in this connection 
to bear in mind that for each complete revolution of the worm 
shaft R, there will a corresponding pencil line (when in con- 
tact), marked on the paper drum horizontally, about one inch in 
length ; consequently, two revolutions mark two inches ; three 
revolutions gives three inches, length of card, &c. 

It must be understood that this calculation of the size of 
pulley O, has reference to engines having low rotative speed, 
say up to 120 revolution per minute, and where a long card is 
desired; but when the speed is increased from this to 500 or 
600 revolutions per minute, the size of the pulley O will have 
to be in accordance with the recommendation (in chapter V; 
in reference to the height and length of diagram advisable, 
where the rotative speeds are gradually increased up to 600 
revolutions per minute, and producing a card two inches in 
length. 

After selecting the pulley required, remove the clutch from 
the worm shaft R, by slacking the set screw shown in collar A, 
and place the pulley thereon, taking care that the pin-hole on 
the inner side of the pulley (not shown in cut), engages with 
the projecting pin A, of the spring case cover S, Fig. 35, then 
replace the clutch on the shaft as far as it will go and secure it 
firmly in place by the set screw in collar A. 



6o Steam Engine Indicator 



& 



Place the indicator in position, and attach the actuating 
cord as already described. 

The tension of the spring in the spring case D, must be 
sufficient at all times to just keep the cord taut, and this may 
be regulated by taking more or less extra turns of the cord 
around the pulley O, until it results in the desired tension. 
The alignment of the Indicator, in order to have the cord run 
evenly, is a matter to be observed ; and if upon starting the 
engine the cord should run unevenly on the pulley O, it may 
be entirely remedied by slacking the indicator connection a 
trifle, and turning the Indicator slightly in the necessary direc- 
tion until a perfect and uniform winding of the cord is ob- 
tained, and which can (by this means) always be accomplished. 

The peculiar construction of the angular teeth on the worm 
shaft R, and also on the drum carrier G, enables each to be- 
come the driver of the other ; that is, on the outward stroke of 
the engine, the drum carrier is driven by the worm shaft; 
while on the return or inward stroke, the worm shaft is driven 
by the drum carrier g, through the action of its retracting 
spring ; said spring always serving to return both of them back 
to their normal positions, at the extreme inner stroke of the 
cross-head, at each revolution while in operation. 

In the absence of a proper understanding of the principles 
of manipulating some of the various Reducing Motions in the 
market, some engineers that have had no particular experience 
with them, look upon all such devices as complicated and gener- 
ally troublesome to operate and are satisfied to continue the 
use of the more antiquated pantagraph and lever movements. 

In our own experience and that of engineers who have 
been using the positive Reducing Gear, described and illus- 
trated in this article, it may be said to have given entire satis- 
faction in all cases, and a return to any of the old methods, 
(after becoming familiar with this) could not be contem- 
plated under any circumstances. 



And Its Appliances, 



61 



CHAPTER VIII. 



DRUM STOP MOTION AND ELECTRICAL APPLIANCE. 



In using the different lever and pantagraph devices, that 
have been illustrated in a previous chapter (or any modifications 
of them), for the purpose of giving motion to the paper drum ; 
it becomes necessary with any and all of them to connect and 
disconnect the actuating cord leading from the device to the 

indicator, in order to start or 
stop the paper drum whenever 
necessary, for either adjusting 
or the removal of the paper 
from the drum. In slow speed 
engines, the matter of hooking 
and unhooking the actuating 
cord is of no great difficulty; 




Fig. 36. 



but with engines of high rotative speed, it becomes more dim- 
cult and requires much more skill and experience on the part 
of the operator to perform the operation successfully and with 



62 



Steam Engine Indicator 




ease. An efficient and very simple attachment, which may be 
adapted to different styles of indicators, for the purpose of 
starting and stopping the paper drum at all times without the 
necessity of unhooking the actuating cord, when used in con- 
nection with any of the pantagraph styles of reducing motion, 
is illustrated in Fig. 36, attached in this case to a Tabor Indi- 
cator ; and whereby the usual handling of the actuating cord 
(that otherwise becomes necessary), to stop the motion of the 
paper drum, is entirely obviated at any and all speeds. 

The device is shown in Fig. 37 detached from the indica- 
tor, and consists of an 
arm A, which may be 
secured to a part X of 
the indicator, by means 
of the set screw B. Up- 
Fig. 37. on the arm A, Fig. 37, 

is a slide C, which may be adjusted to any desired position on 
the arm and secured thereto by the knurled nut E and washer 
F. On the slide C is mounted the cord pulley D for the pur- 
pose of directing the actuating cord (from any form of reduc- 
ing motion), around the said pulley and thence on to the paper 
drum carrier to the indicator. 

The method of determining the proper length of the actu- 
ating cord is as follows : set the slide C, to its extreme inner 
position on the arm A, and place the engine on its extreme 
outer stroke, then bring the cord from the drum carrier around 
the cord pulley D, and thence in the required direction to the 
point of attachment on the reducing motion, which will give 
the necessary length of the actuating cord. At any convenient 
position on the actuating cord and near the cord pulley D, 
there is superposed an elastic band, shown in Fig. 36, for the 
purpose of taking care of the slack of the cord, that will appear 
when the engine is in motion and the paper drum at rest. 
This slack is owing to the length of the actuating cord being 



A u d Its Applia n ces . 6 3 

taken when the engine is at its extreme outer stroke ; conse- 
quently on its arrival at the inner stroke there is an amount of 
cord to be taken care of, equal to the presumed length of the 
indicator diagram, and the intervention of the elastic band is 
for that purpose only. 

While the slide C is at its inner position no motion will be 
transmitted to the paper drum ; but by moving the slide C out- 
ward upon the arm A, it will at once cause the paper drum to 
rotate forward and back, and the slide may be secured in any 
desired position on the arm by means of the knurled nut E, 
therefore in order to start, or stop the motion of the paper 
drum at any time when the engine is in motion, it is only nec- 
essary to change the position of the slide C on the arm A, 
which is accomplished most satisfactorily, by means of the 
knurled nut E. 

To start the paper drum, move the slide outward on the 
arm and secure it by the nut E, and to stop, move it to its ex- 
treme inner position, the actuating cord continuing its usual 
motion during the time the engine is in motion. 

To Take Diagrams Simultaneously. In order to make com- 
plete and reliable tests of steam power from the various com- 
pound and multiple cylinder engines, or whenever it is desirous 
to take diagrams simultaneously from a number of steam cylin- 
ders (in which as many indicators are used), it becomes neces- 
sary to provide some sure means of operating the indicators, 
by which an operator can accomplish the object alone, without 
the aid of assistants and with the certainty that all diagrams 
taken at any particular stroke of the engine or engines, will 
all commence and leave off simultaneously with each other, and 
thereby dispensing otherwise with the number of attendants 
necessary to operate the different indicators at some decided 
upon signal ; a plan whereby an exact coincidence of the dia- 
gram at any particular stroke is very rarely obtained owing to 
the almost impossible concerted action between the operators. 



64 Steam Engine Indicator 

The taking of diagrams from two or more cylinders at the 
same exact stroke of the engine or engines, may be accom- 
plished successfully in different ways that will oft-times, as oc- 
casion requires, suggest themselves to the engineer. An ar- 
rangement sometimes used with fair success, consists of a small 
reservoir of compressed air from which the pressure is com- 
municated to a small piston within a cylinder secured to each 
indicator ; one end of the piston rod being in contact with some 
part of the pencil mechanism, consequently any movement of 
the piston is communicated directly to the said mechanism, 
which results in a contact (when under pressure from the reser- 
voir), between the pencil and paper drum ; and a withdrawal 
of the pencil, (through the action of a spring) when the pres- 
sure is released. These small cylinders are connected to the 
reservoir by means of rubber tubing in which there is a cock 
for admitting and releasing the air pressure upon the piston. 
The operation of the device being about as follows : after seeing 
that the parts are properly connected, start the pencil mechan- 
ism of the indicators in motion, by opening the cock connected 
to each, then by opening the cock from the reservoir the pres- 
sure from that source (through the small piston and its rod), 
will force the pencil in contact with the paper drum and against 
the resistance of the spring. The time of contact between the 
pencil and paper drum is supposed to be during one complete 
revolution of the engine, unless an average card is desired from 
a number of revolutions. The instantaneous release of the air 
pressure against the small pistons, takes place in the act of 
closing the cock ; it being provided with an escape hole for that 
purpose, thereby admitting of the spring to at once move the 
pencil out of contact with the paper drum. 

In the absence of a reservoir of compressed air, the same 
results may be obtained in this device, by using a jet of steam 
through a small pipe leading from the boiler, steam pipe, or from 
any convenient place where a pressure of steam may be 



Arid Its Appliances. 



65 



obtained. Other improvised means depending upon circumstan- 
ces and the ingenuity of the engineer, may be used to produce 
the desired result. The most successful, simple, and satisfactory 

results, may however, be ob- 
tained by the use of the 
electric current. A very neat 
and simple electrical attach- 
ment to enable an operator 
to produce diagrams, from 
any number of cylinders dur- 
ing the same stroke of the 
engine by simply pressing a 
button to close the electrical 
circuit is represented in Fig. 
38, as attached (in connection 
with the reducing motion), 
to the well known Tabor In- 
dicator. 

The attachment consists of 
a specially constructed mag- 
net M, mounted on and secured to a support S, which encircles 
the body of the indicator, and is held in position by the clamp- 
ing screw E. Also secured to the support are the binding 
screws C and the spring D, 
these parts being shown sepa- 
rate from the indicator in Fig. 

39- 

The stud B, Fig. 40, is screw- 
ed into the upright on the 
swivel plate that carries the 
pencil mechanism of the indi- 
cator and serves as a support Fig. 
for the armature A, Fig. 41, and to which it is 
small set screw for that purpose ; therefore any 





secured by a 
movement of 



66 Steam Engine Indicator 




the armature A, in either direction, relative to the magnet M, 
produces a similar motion of the pencil (in the opposite direct- 
ion), to or from the paper drum of the indi- 
cator. 

The spring D, Fig. 39, is formed so as to 
hold the armature within the field of the mag- 
net, before the current is established, and also 
to quickly release it when the current from FlG - 41, 
the battery is broken. The magnet M, consists of a 
g. single spool of soft iron, wound in the usual manner with 
insulated magnet wire, and enclosed by a soft iron shell, the 
combination thereof establishing the two poles of the magnet, 
when subjected to the effect of an electric current passing 
through the wire. The armature A is also constructed of a 
soft grade of iron and is finished to a diameter the same as the 
magnet shell, and is adjustable on the stud B, to exactly coin- 
cide with the magnet M. On the side facing the magnet are 
two small brass pins for the purpose of assisting in the instan- 
taneous release of the armature, from the magnet after the cur- 
rent is broken. This electrical device is easily attached or de- 
tached in a few seconds, and its connection with the indicator, 
does not in any way interfere with the usual manipulations of the 
operator, in adjusting the paper to, or removing it from the 
paper drum ; changing of the springs in the instrument, or any 
minor operations that may become necessary, as the pencil 
mechanism is free to be revolved in any convenient position. 

It is represented in Fig. 38, as being attached to a Right- 
hand Indicator, but it may be used on a Left-hand instrument 
with equal facility. The change from one to the other is easily 
and readily made in the following manner : first unscrew the 
cap (that carries the pencil mechanism), and take it complete 
from the indicator, then by loosening the clamping screw E, 
the support S may be readily removed, and it only remains to 
unscrew the magnet M, from the support S, and change the 



And Its Appliances. 67 

location to directly the opposite side of the support and secure 
it in that position, by means of the small screws for that pur- 
pose. The binding screws, as well as the spring D, will also 
need reversing on the support S ; the parts all being provided 
with means by which it may (if necessary) be easily and readily 
accomplished. Replace the device on the indicator in a re- 
versed position and secure it by the clamping screw E. Where 
the circuit is short the device may be operated in connection 
with a single indicator, by any one of the well known batteries 
in the market, (either dry or liquid). 

In our own experience, and in all cases where such an ap- 
pliance is desired, and where accuracy is necessary, this simple 
electrical device seems to meet all requirements, being easily 
attached or detached, without any change in the mechanism of 
the indicator ; instantaneous in its action, and can be relied up- 
on at all times to give correct results, with the least amount of 
labor and anxiety to the operator. 






6& Steam Engine Indicator 



CHAPTER IX. 



CARE AND USE OF INDICATOR. 



Before attaching the indicator, open the cock and allow 
steam to blow through the pipes for the purpose of removing 
any scale or dirt that may remain in the pipe after fitting up ; 
as it is of the greatest importance that all parts of the indicator 
be kept in good working order, where a close degree of accu- 
racy is expected. The most important of these parts, are the 
cylinder and piston ; to which especial attention should be 
directed as to their condition ; because the accumulation of de- 
posit, or dirt of any description between their surfaces of con- 
tact, (however minute) will produce irregularities, and distor- 
tions in the diagram, to such an extent, as will render it almost 
impossibe to secure the information a diagram is intended to 
convey ; therefore it becomes very essential at frequent intervals 
to remove the piston from the cylinder ; (which can be done by 
simply unscrewing the cap upon which the whole mechanism 
is attached, and lifting from the instrument) and thoroughly 
clean both, by the use of cotton cloth, waste, or some other 
suitable material. 

This being accomplished, lubricate these parts with some 
good cylinder oil, and replace them again in the instrument. 

The pivots or joints of the pencil movement, should also 
be kept clean, and oiled occasionally with some light machine oil 



And Its Appliances. 69 

that will not gum or become sticky ; a bottle of which usually 
accompanies the instruments of all makers. 

This should be used sparingly as a very small amount 
suffices for the purpose, and any surplus should be cleaned off. 

It is absolutely necessary that there be perfect freedom in 
the pencil mechanism ; (and when not subject to the action of a 
spring) the pencil bar on being raised to its highest position, 
should from its own weight, fall with the utmost freedom to 
its lowest position, and this requirement is very essential in 
order to insure correct diagrams. A further test of its correct- 
ness may also be made by again raising the pencil bar to its 
extreme height, and covering (with the thumb or finger) the 
hole through which the steam is admitted against the indicator 
piston ; and if the mechanism be not impeded in any way, ex- 
cept only by the air contained within the indicator cylinder, 
the pencil will descend slowly and uniformly until it reaches 
its lowest position. Should this be found otherwise than as 
stated, it may become necessary to disconnect the parts of the 
movements from the piston, and test each part separately until 
the cause of the trouble is located. 

The Paper Drum also requires attention, it being in 
constant motion, and subject to considerable wear ; conse- 
quently should be examined from time to time, and the 
bearing cleaned, and thoroughly lubricated, using the same 
light machine oil, as for the pencil movement. 

With the ordinary paper on the drum the Siberian lead 
pencil about grade H. H. H. H. should be used in taking the 
diagrams ; the pencil being sharpened to a fine round point 
with a knife or fine file. 

A more satisfactory result of the tracings may be obtained 
by the use of a chemically prepared paper, (called metallic 
paper), upon the drum, and using a point made of common 
brass, or preferably silver wire suitably sharpened for the trac- 
ing point. 



yo Steam Engine Indicator 

One sharpening of the metallic pencil will give good re- 
sults on a large number of diagrams, and the general character 
of the work. will be much more satisfactory than with the lead 
pencil. The paper should be placed upon the drum in such a 
manner that it will be perfectly smooth. This may best be 
done by first folding one end, and slipping it under the longer 
clip ; then pass the paper around the drum and bring the loose 
end under the short clip ; taking the two ends thus located, 
between the thumb and finger, and with the other hand by a 
slight pressure at the top of the card, slide the whole down the 
drum ; the outer edge may then be folded back over the clip if 
needed. 

Adjust the stop screw so that the pencil will bear lightly 
on the paper, otherwise the friction between the pencil and 
card will cause the diagram to be irregular, and will not repre- 
sent the true action of the steam within the cylinder. 

Paper Drum Motion. The motion of the paper drum may 
be derived from various different parts of the engine, but what- 
ever point is selected, it is essential that the motion of the 
drum shall coincide in miniature, exactly with that of the en- 
gine piston, at every part of the stroke. 

Owing to the irregular motion of the engine piston, dur- 
ing the stroke, caused by the varying angularity of the con- 
necting rod, it is often uncertain, and difficult to select a point 
(other than the engine cross-head), that shall fulfill the exact 
conditions required ; but if such other point should be chosen, 
careful attention as to its location becomes necessary, in order 
that the motion resulting therefrom, may in no wise vitiate 
the diagram. 

The Cross- Head being directly connected to the piston 
rod, consequently moves at every part of the stroke, and 
under all circumstances in exact unison with the engine piston ; 
therefore, it is the part usually selected from which to obtain 
the motion of the drum ; as being the most direct, reliable, and 



And Its Appliances. 



71 



convenient for the purpose ; but the amount of its movement, 
(whatever that may be), must be reduced to suit the range of 
the paper drum, or the length of the diagram to be taken ; and 
this reduction must be in an exact proportion, throughout the 
stroke, to the movement of the cross-head. 

Where special reducing wheels are used for this purpose, 
a stud is generally screwed in the cross-head, of sufficient 
length, such as will cause the cord from the reducing wheel, 
when attached, to be in a direct and parallel line with its 
motion. 

It often happens that this plan cannot always be successfully 
accomplished, owing to the various different construction of 
engines ; hence in such cases a resort to the use of small carry- 
ing pulleys will be necessary. 

Carrying Pulleys. It is always desirable to avoid these pul- 
leys wherever possible, as their use are often detrimental ; in 
that they increase the tension on the cord ; cause the cord to 
become dirty from the oil used in lubricating the pulley ; 
which will in a short time render it unfit for further use ; they 
also create a friction that becomes an additional 
tax upon the drum spring, and in many ways 
becomes a source of annoyance to the opera- 
tor. 

Nevertheless occasions often occur, where 
their use becomes indispensable, and in such 
cases they should be located at such points, as 
will suggest themselves to the ingenuity of the 
engineer, as best, for obtaining the desired re- 
sults. The style shown in Fig. 42 is universal 
and meets all requirements. 

Various devices, and methods for reducing 
the amount of movement of the engine cross- 
head to any desired length of diagram, will be found repre- 
sented aud described in Chapters 5, 6 and 7. 




Fig. 42. 



72 Steam Engine Indicator 

The Indicator Cord. The usual manner of imparting- mo- 
tion from the engine cross-head to the drum, is through the 
medium of a hard braided linen cord ; and sometimes a metal- 
lic cord (such as fine piano wire), may be used to advantage in 
connection with it, under circumstances where an unusual 
length of cord is required. 

Cord of all kinds especially when new, is possessed of a 
certain amount of elasticity, of which it becomes necessary to re- 
move as near as possible, before using, in order to avoid any 
further stretch when in use ; so that coincidence of motion be- 
tween the cross-head, and the reduced motion of the paper 
drum shall be practically uniform. 

The most simple and ready method, and the plan usually 
adopted for removing this elasticity is by suspending the cord 
from one end, and attaching sufficient weights to the other; 
allowing it to remain so suspended from 12 to 24 hours; or un- 
til it becomes apparent that any further stretching may result 
in injury to the cord. 

The cord that is intended especially for indicator work is 
usually stretched by the manufacturers until its elasticity is 
eliminated, and therefore will not stretch, when in use under 
ordinary circumstances, to any extent that would seriously in- 
terfere with the accuracy of the diagrams. 

A simple, light, and exceedingly convenient cord adjust- 
er is represented in Fig. 12, Chapter IV, for adjusting the 
length of the cord between the indicator and reducing gear. 

The hook on the cord from the indicator, should be at- 
tached as close to the indicator as possible ; (to prevent any 
swaying of the cord), and connect into the ring of the cord ad- 
juster, while the small holes in the adjuster receive the cord 
from wherever the motion is derived. 

The Indicator Spring. The denomination of the spring to be 
used in any particular case, depends principally upon the boil- 
er pressure. A book usually accompanies most indicators, 



And Its Appliances. 73 

which gives the necessary information, (either by a table di- 
rect, or by a computation rule), for the selection of the most 
suitable denomination of spring, for any given boiler pressure. 

In indicators which have a range of pencil movement of 
from 2^ to 3 inches in height, a 40 pound spring is a good 
standard for pressures between 80 and 90 pounds, and a 50 
pound spring for boiler pressures from 100 to 120 pounds per 
square inch. Each indicator spring is numbered to correspond 
with the pressure per square inch required to compress it an 
extent, sufficient to cause a vertical movement of the pencil of 
exactly one inch. 

For example : In case a 50 spring, as shown in Fig. 13, 
Chapter IV, is used, a pressure of 50 pounds per square inch 
in the engine cylinder, will raise the pencil one inch, or a 
pressure of one pound will raise the pencil T V of an inch ; the 
same rule applying to all other denomination of springs. 
After use, the spring ought never be allowed to remain in the 
instrument, but should at once be removed, and wiped perfect- 
ly dry ; otherwise it is liable in a very short time to become 
corroded and pitted to such an extent, as to render it quite in- 
accurate ; at the same time the inside of the indicator cylinder 
and piston, should also before laying away be made perfectly 
clean, and free from all moisture arising from condensed 
steam. 

Clean by means of cotton waste, or cloth, used in connec- 
tion with a wooden stick. 

H|llll|lllllllll|lllllllll|llll|llll|HII ^ 

■0 40 80 120 160 

40 TO THE INCH 



Fig. 43. 

Indicator Scales. For convenience and greatly facilitating 
the measuring of the diagrams, special boxwood scales, as 
shown in Fig. 43, are provided, upon which the inches are 



74 Steam Engine Indicator 

divided into units; each unit representing pounds pressure 
per square inch, corresponding to the number of the spring in 
use. 

The edge upon which the graduations are performed, 
is beviled, in order that the marking may be near the paper, 
and consequently be more readily observed ; hence their use 
will be found much more convenient, than the steel scales 
sometimes in use. 

The Drum Spring. The tension on the drum spring illustrat- 
ed in Fig. 44, is a matter that depends upon the good judg- 
ment of the engineer, and should be just suffi- 
cient to keep the cord taut on the backward 
or inner stroke of the engine. The best re- 
sults are obtained where the highest tension 
Fig. 44. i s employed, consistent with good work. As 

the speed of the engine is increased, it is sometimes necessary 
to increase the tension on the drum spring to counteract 
the effect due to the inertia of the drum at the higher speed, 
and provisions are usually made on most indicators, and in- 
structions given whereby the tension on the spring may be 
varied to suit the higher speeds wherever necessary. 







And Its Appliances. 75 



CHAPTER X. 



TO TAKE DIAGRAMS. 



The desired pressure spring being placed in the instru- 
ment, and the paper in place upon the drum, connect the cord 
from the indicator to whatever form of reducing motion there 
may be at hand, (thereby starting the drum in motion), then 
open the cock on the pipe communicating between the steam 
engine cylinder and the indicator piston, (which in turn starts 
the pencil movement) until a few revolutions of the engine 
have been made, or until the instrument is heated to a temper- 
ature due to the steam pressure present. During this motion, 
examine the pencil mechanism to see that it is moving freely, 
which may be ascertained by placing the finger directly against 
and over the top of the piston rod, and by following its motion 
up and down ; the presence of any grit between the indicator 
cylinder and its piston, can readily be detected. If such 
should be found to be the case it will be necessary to stop the 
motion of the indicator, and remove the pencil mechanism 
with the piston and thoroughly clean and oil, before again 
replacing in the indicator. Again set the Indicator in motion, 
and after a few revolutions of the engine have been made, 
swing the pencil until it comes in contact with the paper on 
the drum and hold it there during one complete revolution of 
the engine. Withdraw the pencil and close the indicator 
cock, and immediately return the pencil to the paper 
in order to trace the atmospheric line. This should always 
be done as soon, as possible after tracing the card, so that 



y6 Steam Engine Indicator 

it may be drawn under about the same conditions (as to 
temperature, etc.) as when the card was taken. When 
power is to be measured, it is a good plan to keep the 
pencil in contact with the paper during a number of revol- 
utions of the engine ; and in measuring the diagram, to take a 
line most nearly representing the average. Diagrams should 
always be taken from both ends of the cylinder where correct 
conclusions are expected. 

Although a diagram from one end of the cylinder may 
prove satisfactory, it is not safe to infer that one from the 
opposite end will be equally so ; but on the contrary there will 
often be found a great difference between diagrams taken from 
each end of the cylinder, owing to the varying conditions of 
pressure, etc., usually found in practice. Very often this 
difference results from improper or uneven valve setting; 
wherein the period of opening or closing the valve, and also 
the point of cut-off differ at each end in relation to the stroke 
of the engine ; and may be partly due to rough and tortuous 
steam passages. 

Sometimes the load may suddenly change during the in- 
terval between the taking of the first and second diagram, 
causing a disparity between them that might prove misleading, 
in that, it would give the appearance similar to that of an un- 
even valve adjustment, consequently after a careful consider- 
ation from a number of diagrams, it becomes a requisite of the 
engineer to use his best judgment in deciding the cause 
and applying the remedy for any irregular or unusal appear- 
ance of the diagram. This information can only be derived 
from a careful application of the indicator and a study of the 
diagrams. 

Where two indicators are used and placed at each end of 
the cylinder, the diagrams (if desired) may readily be taken 
simultaneously; but in case of only one indicator at hand, it 
must be changed from one end of the cylinder to the other; 



And Its Appliances. yj 

in order to obtain diagrams from both., a matter requiring 
considerable time and trouble; therefore it will be found most 
convenient in such case to place the indicator in connection 
with a three-way cock (previously described), at the middle of 
the cylinder, thereby admitting steam from each end, so that 
diagrams can be taken from either end of the cylinder, by 
simply turning the handle of the three-way cock to the required 
position. This arrangement greatly facilitates the labor, and 
it also enables the operator to produce diagrams from each end 
of the cylinder, upon the same sheet of paper, and in the short- 
est possible time ; it being very essential that the second 
diagram be taken as quickly as possible after the first, in order 
that the conditions of speed, load, and pressure may remain 
more nearly alike during the time occupied for both tracings. 

It is also more satisfactory to the engineer to take diagrams 
from both ends of the cylinder, upon the same paper as it en- 
ables him at once to make a discernable comparison of the pres- 
sures exerted on the opposite sides of the piston, throughout 
one revolution of the engine . After all required ad j ustments, that 
become necessary have been made, and a satisfactory diagram 
obtained, stop the motion of the drum and remove the paper 
therefrom. Make memorandum on the paper of as many of 
the facts, as may be required, such as the style of engine, 
where located, the diameter of cylinder, length of stroke, 
diameter of piston rod, the number of revolutions per minute, 
which end of cylinder, the scale of the spring, the vacuum 
in the condenser, the boiler pressure, the day and hour of tak- 
ing the diagram, and any other factors that may enter into, 
and become necessary for an accurate consideration and solu- 
tion of the diagrams. 

For convenience of writing in the data, and also for filing 
away for future reference, the paper used upon the drum is us- 
ually in the form of printed blanks of suitable dimensions to 
fit the drum of the indicator, for which they are designed, and 



73 



Steam Engine Indicator 



contain the heading of the different principal factors necessary 
for computing from the diagram, the horse power, water con- 
sumption, etc., of the engine. For very expert tests, these 



_ _ Engine at _ _ 

:,- Diameter, of Rod ; Stroke ■'.. ; Clearance- 

IS- .; Time ; End of Cylinder. ; Scale of Spring.. 

Boiler Gauge ; Vacuum Gauge ^ ; Rfiv^per minute . 

Styled Indicator — __ ; K£. ft.. . , ; l.rLP.. ^_ „._».„; 



Diagram from 

Diameter of Cylinder.. 
Date •_. 




Fig. 45. 

blanks may be printed in various forms, to suit any required 
data necessary ; but the above as shown in Fig. 45 will be found 
sufficiently elaborate for any ordinary indicator practice. 



9k 



A nd Its Appliances. 



CHAPTER XI. 



INDICATOR DIAGRAMS, 



The important and essential knowledge to be derived from 
a careful investigation and study of indicator diagrams is in- 
valuable to the engineer, as they enable him to easily ascertain 
and establish various facts concerning the use of steam, that by 
any other method would prove complicated and unsatisfactory ; 
of which the following may be stated. 

First. It shows whether the valves of an engine are cor- 
rectly and evenly timed ; and also serves as a guide in all 
necessary adjustments of the same that may be required, in 
order to insure the best distribution of the steam working with- 
in the cylinder ; and thereby securing the maximum economy, 
and efficiency of the engine. 

Second. The indicator power developed in the cylinder of 
an engine, may be determined ; also the quantity of power lost 
in various ways ; such as leakage of valves, back pressure, too 
early release, and incorrect adjustment of valves. 

Third. It indicates whether the steam ports, and passages 
are adequate in size, and a diagram taken from the steam chest, 
will also show whether the steam pipe and its connections are 
of sufficient size. 

Fourth. It indicates the condition of the valves and pis- 
ton in reference to leakage. 

Fifth. In connection with a feed water test, (showing the 
actual amount of steam consumed) the economy with which the 
engine works may be determined. 



So Steam Engine Indicator 

To ascertain with accuracy, each and every item of infor- 
mation here mentioned, it is absolutely essential that the dia- 
gram should truly represent the motion of the piston ; and also 
the pressure exerted on both sides of it, at every point of its 
stroke. 

The general features of a diagram, that indicates a proper 

distribution of the steam in an engine cylinder, is represented 

in Fig. 46, the attainment of which, (as near as possible) 

should be the endeavor of an engineer in setting the valves of 

3 




A 

Fig. 46. 

his engine. A. A. is the atmosphere line, and B. B. represent- 
ing boiler pressure. 

In this diagram the initial steam pressure, which is the 
highest pressure realized in the cylinder, is fully maintained up 
to the commencement of cut-off ; indicating ample size of steam 
pipes, ports, and other passages in the engine. 

The expansion curve is good, and the release of the steam 
is sufficiently early to secure a free exhaust, also low, and uni- 
form back pressure. 

The exhaust valve closes on the return stroke, in time to 
provide the necessary compression, (or cushion), and thereby 



And Its Appliances. 8 1 

counteracting- in part the effects of enertia and momentum of 
the piston, cross head, and other reciprocating parts, at the end 
of the stroke. 

The admission of steam takes place promptly ; and projects 
the admission line to initial pressure at right angles (or per- 
pendicular) to the atmospheric line. 

These qualities in a diagram being an especial requisite 
under any circumstances, to insure an economical working 
engine. 

In practice however, there will be a great difference in the 
outline and appearance of the cards from different engines, 
and even from the same engine ; arising from numerous cir- 
cumstances and conditions connected with it. 

The diagram as before stated simply shows the pressure of 
steam existing in the cylinder at each part of the revolution of 
the engine, and it is the province of the engineer to determine 
whether these pressures at each and every point are the correct 
ones ; and if such is not the case to ascertain wherein the fault 
lies, that causes the error; then determine upon, and apply the 
remedy. 

It must be understood, that in a great majority of cases, 
the shape or outline of the diagram, depends principally upon 
the manner in which the steam is admitted to, and released 
from the engine cylinder. 

Therefore, by careful investigation and measurement of 
these outlines, and turning the varied information which they 
furnish to practical advantage, the real value of the indicator is 
readily made apparent. 

As a preliminary to the study of the diagrams, suppose we 
knew that at a certain part of the stroke the full boiler pressure 
should be realized ; now if this does not appear to be the case 
on the diagram there is evidently imperfections existing, either 
from an incorrect adjustment of the valves, or may be due to 
inadequate capacity of the steam pipes, and passages between 



82 Steam Engine Indicator 



the boiler and engine cylinder ; and almost invariably happens 
also with engines having insufficient, or extremely light loads. 

Adversely, the diagram may show too great a pressure, at 
other certain points, when we know that there should be less in 
order that the demands for good economy and efficiency in the 
engine be obtained. 

This latter circumstance may also proceed partly from in- 
correct valve adjustment ; although it is principally caused by 
leakage through the admission valves after cut-off ; in combina- 
tion with the re-evaporation of steam previously condensed 
within the cylinder in the early part of the stroke. 

Any derangement of valve mechanism of the engine, such 
as incorrect position of the eccentric, on the shaft or an uneven 
adjustment in the length of the valve rods and connections, 
will in consequence, be revealed in the diagram, by late admis- 
sion or release, by low initial, or high back pressure, also by 
absence of compression ; either of which in performing an equal 
amount of work will result in an increased consumption of 
steam. 

Consequently where discrepancies of any kind occur, a 
thorough investigation, study, and reasoning of the diagram 
first becomes necessary, in order to intelligently locate the 
cause of the defect, and make changes, and corrections accord- 
ingly until the diagram shows a proper distribution of steam 
pressure throughout the stroke of the engine. 



dfc 



And Its Appliances 83 



CHAPTER XII. 



STUDY OF DIAGRAMS. 



To the Steam Engine Indicator (it may be said), belongs 
the credit of furnishing a great part of the information that 
has enabled scientific engineers, (and others who have studied 
the subject) to apply intelligently and successfully, and has 
hereby contributed in a great measure to the present perfec- 
tion of our modern steam engines. 

The most correct and best means of obtaining a knowledge 
of the internal workings of the steam in a cylinder under differ- 
ent circumstances of loads and pressures is, by a careful study 
of what are designated as Indicator Diagrams. 

A diagram from one end of a steam engine cylinder shows 
the exact pressure acting upon the engine piston, at any and 
every part of its movement, during the time of one complete 
revolution on both forward and return stroke of the engine ; 
and to show a corresponding pressure on the other side of the 
piston, another diagram must be taken from the opposite end 
of the cylinder. 

The outline of the figure traced by the pencil upon the paper 
of the indicator drum, depends upon the variable pressure of 
steam in the cylinder, acting upon the engine piston, through- 
out one complete revolution of the engine, in combination 
with the horizontal length of the figure produced by the rota- 
tive motion of the paper drum. 



84 Steam Engine Indicator 

If the steam be admitted to the cylinder at the commence- 
ment of the stroke and continued at a uniform pressure, and 
exhausted at the extreme end, and from thence returning to 
its beginning, it will have traced a figure on the paper, bearing 
a close approximation to a parallelogram, or rectangle. 

If the admission of steam had been cut off, after only a 
part of the stroke had been completed, (leaving the amount to 
expand to the end of the stroke) the diagram will assume a 
shape somewhat similar to that represented in Fig. 47. 

In the matter of 
details these two rep- 
resentative forms may 
have innumerable 
modifications. 

We have selected 
Fig. 47 as exhibiting 
the essential features 
.and events (during 
the stroke of the en- 




H 1 

Fig. 47. g me )> 01 a well pro- 

portioned diagram, showing the action and pressures of steam 
that usually take place in the engine cylinder. This diagram 
shows that the admission of steam commences at A and con- 
tinues to the point C, where cut-off commences, and is com- 
plete at D ; the expansion is from D to E ; the exhaust begins 
to open at E and closes at G; the back pressure is represented 
by the line from F to G, and continuing to A. The compres- 
sion of the steam remaining after the exhaust closes, begins at 
the point G, and ends at the admission line A, B; this com- 
pression producing a continual increasing back pressure to the 
point A. 

The point T is where the expansion line would have 
reached provided the exhaust had remained closed to the end 
of the stroke, and is designated the Terminal Pressure. 



A 7id Its Appliances. 8 5 

The line H, I, represents the atmospheric line ; and the 
different events of the stroke, appearing on the diagram at 
various heights above the atmospheric line are measured from 
that line, in. pounds pressure by a scale corresponding with the 
spring used, in producing the diagram ; and consequently the 
location of these points in reference to each other, becomes an 
index to the engineer, and serves as a guidance to him, in the 
study of engine performance and in the steam economy of 
engines. 

It is advisable in most cases to take the diagrams from both 
ends of the cylinder, on the same sheet of paper, as shown in 
Fig. 48, (by the use of the three-way cock, as recommended in 

a former chapter)in order 
to facilitate the matter 
of making a comparison 
between the diagrams 
from each end of the 
cylinder, more readily, 
and thus showing the 
varying pressure at dif- 
ferent events of the 
stroke, in both ends of 
the cylinder; such as 

Reproduction of an actual card taken from a 9^ in. x 9 J , 

Westinghouse engine— 325 revolutions per minute. admission of Steam, 

point of cut-off, release, or opening of exhaust, closure of ex- 
haust, compression, etc., and thereby showing any errors or 
discrepancies in the adjustment of the valve, or valves, that 
regulates and controls the flow of steam to and from each end 
of the steam cylinder, and which thereby enables the engineer 
to arrive at correct conclusions in reference to faulty valve mo- 
tions and methods of correcting them ; which by any other way 
is a difficult task to accomplish, with any certainty, that the re- 
quirements of a correct valve motion are attained. 




Fig. 48. 



86 Steam Engine Indicator 

An Indicator Diagram is the result of two movements, 
which are at right angles to each other ; one of which is the 
rotation of the paper drum, forward and back, around its cen- 
tral stud, and is produced on a reduced scale, coincident with 
and by the movement of the engine cross-head, and thereby 
tracing a horizontal line on the paper drum, at any time a con- 
tact is made between the drum and pencil. 

The other is the vertical movement of the pencil, parallel 
to the axis of the drum and is produced by the steam pressure, 
acting on the piston of the indicator, and forcing it to a height 
proportionate to the pressure upon the piston ; consequently 
the length of the diagram represents the stroke of the engine 
on a reduced scale ; while the vertical height at any given 
point, represents the pressure upon the Indicator piston, at a 
corresponding point in the stroke of the engine. 

The height to which the pencil will ascend, depends en= 
tirely on the pressure exerted upon the piston, and the denom- 
ination of the spring used, and is measured in pounds 
pressure per square inch, at any given point in the length of 
the diagram, by a scale, or rule, divided in a number of units 
per lineal inch, to correspond with the denomination of the 
spring. 

The denomination or number of any particular spring, is 
one that requires the" same number of pounds pressure per square 
inch on the indicator piston, to compel the pencil to move one 
inch in vertical height, against the resistance of said spring. 

By placing a spring in the indicator and connecting the cord 
so as to give motion to the paper drum, (and before admitting 
steam to the instrument) a horizontal line may be drawn, by 
bringing the pencil in contact with the paper on the drum. 

This line is called the atmospheric line, and from which, 
as a zero line, all pressures are measured in a vertical direction 
from the same, whether above or below the line. All 



And Its Applian ces. 87 

measurements above the atmospheric line represents positive 
pressure, while below the line, show negative pressure. 

For each indicator spring, there is usually provided a 
special scale, or rule, for the different denominations. For 
example : A diagram that has been taken where a No. 40 
spring was used in the indicator, (designated a 40 pound 
spring) should be measured by a scale that is divided in 40 
parts to each lineal inch ; each division in vertical height, 
above the atmospheric line representing one pound pressure 
per square inch on the indicator piston. 

In the various computations and study of diagrams, for 
the purpose of ascertaining the Mean Effective Pressure on the 
Engine Piston; Horse Power; Steam Consumption, &c, and 
also for plotting the hyperbolic curve, it becomes necessary to 
establish what is called the vacuum line, or line of no pressure, 
which should be located parallel with the atmospheric line, 
and at a distance below it, equal to 14.7 pounds, by the scale 
corresponding with the scale of the spring with which the dia- 
gram was taken. 

Another and important factor pertaining to the same 
study, is the clearance line, which is drawn perpendicular to the 
atmospheric line and located at the steam admission end of the 
diagram; and at such distance from it, as will bear the same 
proportion to the length of the diagram, as the volume of the 
clearance space bears to the piston displacement ; or that vol- 
ume which is equal to the area of the steam cylinder multiplied 
by the stroke of the piston. 

The clearance is the amount of waste room between the 
steam valve and the engine piston when at its extreme end of 
the stroke, and which has to be filled with steam at initial 
pressure at each end of the cylinder, for every revolution of 
the engine. 

The required amount of steam for this purpose comes 
either directly from the boiler, or, by the compression of the 



88 



Steam Engine Indicator 




steam that remains in the cylinder after an early closure of the 
exhaust valve, or from both combined. The amount of clear- 
ance varies in different styles of engines. In slow running 
engines, this variation usually amounts to from two to five per 

cent. , whereas for high 
speeds it may reach 
from two to ten or 
twelve per cent., or 
even more. 

The finding of the ex- 
act amount of the clear- 
ance (in the absence of 
any data fiom the man- 
ufacturer of the en- 
gine), is often a diffi- 
7r<4CW?12 l. '*£ cu lt matter, but may be 

FlG « 49. roughly approximated 

in most cases, either by computation from measurements of 
the space between the valve and piston, when at its end of 
stroke ; or it may be 
accurately deter- 
mined, (where the 
valves and piston are 
tight) by filling the 
space with water from a 
receptacle containing a 
quantity that has been 
previously weighed or 
measured, and its vol- 
ume ascertained. In 
many cases however 
this is not practicable, 
and is almost impossible, with engines that have been in use 
and neglected until the valves and piston become leaky, and 




yOfC 4S£f*'A % l. /ATS. 

Fig. 50. 



And Its Appliances. 



8 9 



thereby preventing any chances of accuracy in the matter. 
Sometimes the only knowledge regarding the amount of clear- 
ance has to be obtained from the diagram itself. 

If this has well denned expansion and compression curves 
the clearance line on the diagram may be closely determined, 
by a graphical method, from either curve; as shown in Figs. 
49 and 50 as follows; Select two points, (preferably) on the 
compression curve, Fig. 49, as far apart as possible, but within 
the limits of the true curve, and draw a line connecting the 
two points, which will represent one of the diagonals of a rec- 
tangle described on the curve, of which two sides are parallel 
to the atmospheric line. 

If now a diagonal be drawn through the opposite corners 
of the rectangle and extended to the vacuum line ; then a per- 
pendicular drawn from the point of intersection, will be the 
approximate clearance line ; and the distance of this line from 
the end of the diagram, divided by the total length of the dia- 
gram will give the percentage of clearance in the engine. 

Another method 
of approximately as- 
certaining the clear- 
ance is shown in Fig. 
5 1 , the results of 
x which coincide exact- 

ly with Fig. 49, but 
is given as being 
rather more simple in 
its application. 

Draw the straight 
I line A. E. from a point 
** on the vacuum line 
(as at A.) in a direc- 
tion as will cut the compression curve at two points B. and C. 
and continue it beyond the end of the diagram as at E. Now 




Fig. 51. 



90 ozeam Engine Indicator 

with a pair of dividers, set one leg- on the point A. and adjust 
the other to point B. and with this distance so taken, place 
one point of the dividers on point C. and describe a line inter- 
secting the line A. E. at D. 

If a perpendicular be now drawn from the vacuum line 
through this intersection, then its distance from the end of 
the diagram will represent the clearance of the engine. 

The amount of clearance in an engine is an important fac- 
tor, and is always considered in the study of steam economy 
as a source of loss ; therefore in the designing of the various 
styles of engines, it has always been one of the principal in- 
tentions with engine designers, to construct them with a view 
of reducing the clearance to a minimum and thereby saving 
(in a measure) the amount of steam required to fill large clear- 
ance spaces. 

A reduction of clearance has an effect to produce a lower 
terminal pressure, for any given cut-off; and also greater 
mean effective pressure for a given terminal ; both of which 
are conducive to good economy. 

A loss takes place from the clearance, when the steam is 
exhausted at a higher pressure than the back pressure, or, that 
pressure which exists on the return stroke and consequently a 
reduction of clearance, also reduces this loss of steam, 



ate 



And Its Appliances. 91 



CHAPTER XIII. 



LINES AND POINTS OF THE DIAGRAMS. 



The diagram shown in Fig. 52, is presented in this chap- 
ter, to more fully designate by name the various lines, points, 
and curves, that in combination serves to make it complete, 
and also shows the lines dotted, that in most cases become nec- 
essary to be added by hand, in order to assist, and facilitate in 
all matters attending the accuracy of any calculations that may 
arise in reference to indicator diagrams. 

The following names are generally applied to the various 
lines and curves of the diagram. 

H. I. is the Atmospheric Line, and is traced by the indicator 
at a time when communication between the engine cylinder, 
and indicator piston is closed, and the atmosphere having free 
access to both sides of the piston of the indicator. 

V. V. is the Vacuum Line, drawn by hand in dotted lines, 
and represents the line of perfect vacuum or absence of all 
pressure. 

It is drawn I4 T V pounds, (by the scale of the spring with 
which the diagram is taken) below the atmospheric line ; that 
being the mean pressure at sea level. 

V. K. is the Clearance Line, shown drawn by hand in 
dotted lines, at such a distance from the end of the diagram, 
as will represent the total clearance or waste room between the 



9 2 



Steam Engine Indicator 



face of the valve, and the piston, when the engine is at either 
extreme end of the stroke. 




?H T 



Fig. 52. 

Its distance from the diagram is usually reckoned in per 
cent, of the piston displacement, and in Fig. 52, shows about 
4 per cent, of clearance. 

A. B. is the Admission Line, and its height above the at- 
mospheric line represents the pressure due to the admission of 
steam to the engine cylinder. 

• It is usually very nearly perpendicular to the atmospheric 
line, for the reason that the admission of steam takes place 
very quickly, and at a time when the piston of the engine is 
moving very slowly, or nearly stationary. 

B. is the point of Initial Pressure and is the first pressure 
realized at the beginning of the stroke of the engine. 

B. C. D. is the Steam Line, and is traced during the time 
the steam is being admitted to the cylinder, or until cut-off 
takes place. 



And Its Applia?iees. 93 

D. is the Absolute Point of cut-off and is the point where 
the valve closes and thereby prevents any further admission of 
steam to the engine cylinder. 

Owing- to their peculiar formations, many diagrams do not 
show clearly, (from observation alone) the exact point. 

D. E. is the Expansion Curve, and represents the gradual 
fall of pressure due to the expansion of the steam remaining 
in the cylinder after cut-off takes place, and continuing to the 
end of the stroke. 

E. is the Point of Exhaust, and is located where the exhaust 
valve begins to open ; thereby releasing or exhausting the 
steam from the cylinder ; and like the point of cut-off, is some- 
times difficult of exact location. 

E. F. is the Exhaust Line, which descends suddenly and is 
traced during the interval that occurs, between the time the 
exhaust valve begins to open, and the end of the stroke. 




H I 

Fig. 53. 

In diagrams like Fig. 53, where the pressure has gradu- 
ally fallen during expansion, sufficiently low, to coincide with 
the return or back pressure, this line does not appear. 

And in diagrams like Fig. 54, where the expansion curve 
falls below the back pressure, before the end of the stroke, 



94 Steam Engine Indicator 

(causing a partial vacuum in the cylinder thereby), the exhaust 
line is ascending until it agrees with, and merges into the back 
pressure line. 




Fig. 54. 

This action indicates a rapid flow of the steam from the 
exhaust pipe, back into the cylinder; thereby restoring the 
pressure lost through the expansion curve falling below the 
back pressure line, during the latter half of the stroke. 

F. G. is the Back Pressure Line, and represents the pres- 
sure opposing the piston on its return movement, and for this 
reason is called Back Pressure. 

In diagrams from non-condensing engines it either coincides 
with, or is above the atmospheric line ; while in condensing en- 
gine it is below the atmospheric line, at such a distance as cor- 
responds with the vacuum obtained in the engine cylinder ; 
and in either case it acts as back pressure. 

G. is the point of Exhaust Closure, and is where the ex- 
haust valve closes ; thereby preventing the further escape of 
the steam from the cylinder. 



And Its Appliances. 95 

Like the point of cut-off and exhaust, it cannot in all cases 
be located very exactly from observation ; on account of the 
change of pressure, due to a more or less gradual closing of 
the valve, which will cause its exact location to be rather 
undefined. 

G. A. is the Compression curve, and is a result of the rise 
in pressure due to the compression (from the return motion of 
the piston), of the steam remaining in the cylinder, after the 
exhaust valve closes. 

In cases where the exhaust remains open until the end of 
the stroke, this line does not appear on the diagram. 

T. is the point of Terminal Pressure, and is an indispensa- 
ble factor in many calculations pertaining to diagrams. 

It may be located by a continuation of the expansion curve 
from E, to the end of the diagram at T, as shown in Fig. 52, 
and its height above the line of perfect vacuum, V. V. repre- 
sents the absolute pressure that would exist at the end of the 
stroke ; providing the release of the steam in the cylinder does 
not take place earlier. 

This pressure is always measured from vacuum line V. V. 
hence it is the absolute Terminal Pressure. 

Initial Expansion, is the fall in pressure that takes place 
through expansion during the interval between the admission 
of steam, and absolute point of cut-off. 

It is represented in the diagram, Fig. 52, by the dotted 
line B. P. and is generally considered an undesirable feature, 
especially in automatic cut-off engines. 

T. 1. and T. 2, in dotted lines, are made use of in calcula- 
tions connected with the water or steam consumption of the 
engine, per indicated horse power, as shown by the diagram ; 
and which will be referred to hereafter. 

The Mean Effective Pressure, as before noted, is the differ- 
ence between the average of all the varying pressures acting 
against the engine piston, in impelling it forward; and that of 



g6 Steam Engine Indicator 

all the average pressure which tends to retard its motion ; and 
is another indispensable factor in the computations of the dia- 
gram ; and is expressed thus: M. E. P. 

The point of cut-off is an important event in the stroke of 
the engine, and is located at a place on the diagram, where the 
steam valve absolutely closes; as at D, Fig. 52, and thereby 
prevents the further admission of steam to the cylinder during 
the stroke. 

With slow speed engines, and quick releasing gear, the 
point of cut-off will be fairly well defined ; but with the higher 
speeds, relative to the time, or period required from the com- 
mencement, to the absolute closure of the valve, it will enable 
the piston to travel a certain distance during that time, (more 
or less according to circumstances) and which will cause the 
steam line to be rounded off, to meet the expansion line, and 
consequently the point at which the valve actually closes, can 
only be approximately determined by noting the point at which 
the curve from the steam line changes and begins to concave 
inward; thence continuing on, to exhaust opening, thereby 
forming and completing the expansion curve. 

In many cases it is almost impossible to determine the 
point of cut-off even in this manner, owing to the various dis- 
torted formations of the lines of the diagram near this point. 









And Its Appliances. 97 



CHAPTER XIV. 



ISOTHERMAL CURVE. 



A careful comparison and examination of the hyperbolic 
curve, with the expansion curve of a properly jacketed steam 
cylinder, with tight piston and valves, has demonstrated that 
the two curves conform with each other very nearly, in all re- 
spects ; therefore assuming that the expansion line should be 
a hyperbolic curve, then the principle, upon which this curve 
is constructed, furnishes an easy and ready method of locating 
the theoretical point of cut-off, for any particular point select- 
ed on the expansion line of the actual diagram. The hyper- 
bola, sometimes called the Isothermal curve, is constructed on 
the principle established by Mariotte, in reference to the com- 
pression of gases, and known as the Mariotte law ; and is gen- 
erally expressed as follows : 

"The temperature remaining the same, the volume of a 
given mass of gas, is in inverse ratio to the pressure which it 
sustains. And this may be held to be substantially correct 
within a considerable range of pressure ; therefore according 
to this law, if steam of 100 pounds absolute initial pressure, 
per square inch, be admitted to a steam engine cylinder (ignor- 
ing clearance in the matter), during one-half of the stroke, and 
admission stopped at that point ; and allowing the volume at that 
pressure to expand during the balance of the stroke, the vol- 
ume will be doubled, with a reduction of pressure, of one-half, 



9 8 



Steam Engine Indicator 



or 50 pounds per square inch at the end of the stroke. If, in 
this example, the admission of steam had been stopped at one- 
quarter of the length of the stroke, the volume of that amount 
of steam at half-stroke would have been doubled, but with a re- 
duced pressure of one-half, (or 50 pounds per square inch). 
At three-fourth stroke, the volume would be three times, at 
one-third pressure (or 33^ pounds), and at the end of the 
stroke, the volume would be increased four times, and result 
in a pressure of one-fourth initial (or 25 pounds per square 
inch), hence, the distance from the clearance line of a diagram, 
to any point on the expansion line, if multiplied by the pres- 
sure at such point, the product will be the same wherever loca- 
ted, and this fact furnishes a simple rule for determining any 
number of points through which the curve must pass, by tak- 
ing the product of any point, (by such multiplication), as a 
constant number, and dividing it by other distances from the 
clearance for corresponding pressures, or by other pressures 
for distance from the clearance line. The properties of the 
hyperbola therefore enables us to locate points on the curve by 
an arithmetical method, described and represented in Fig. 55. 

A 4 B 







> 


\ 


















V 




^"""^^— ^*> M 




V 




















' , 


--- 


£ 


H 




=a 


u 


<3 


^ 


.«*> 


'«? 


"» 


^ ^ 


'<% 


X 








% 


K 


X) 


** 


^ 


*-J 


«S 


*> n *i 







V ■' '^2 4 



Fig. 55. 



8 ? 



fO Jf /£. 4% 



First draw the absolute vacuum, or zero line V, at a distance 
equal to 14.7 pounds by the scale of the spring below, and 
parallel, with the atmospheric line H. I. Then locate the 
clearance line K, in accordance with the best data at hand, in 



A nd Its Appliances. 99 

reference to what its distance should be from the end of the 
diagram. 

Draw A, E, to represent the boiler pressure. Select the 
point of cut-off on the diagram (as near as possible from obser- 
vation, as at X), and draw a line through it, perpendicular to 
the vacuum line, and intersecting it at point 3, and the line A, 
E, at C, and this line is called the cut-off line. The point .C, 
will then be the commencement of the hyperbolic, or theoreti- 
cal curve. The vertical height of the line 3, C, (above the 
zero line), represents the pressure of steam, at the point of cut- 
off C ; the diagram showing that pressure to be 100 pounds per 
square inch, (measured by the scale of the spring No. 80). 
The distance from the clearance line K, to cut-off line 3, C, 
will represent its volume. 

Divide this volume, or distance, into any convenient num- 
ber of equal parts, (it is shown divided into three parts in Fig. 
55), then take the length of one such division, and (with a pair 
of dividers, or otherwise), commencing at the clearance line K, 
space on the vacuum line whatever number of these equal di- 
visions, that may be contained in the length of the diagram, 
and erect perpendicular lines (a little above the actual curve), 
from each division. These lines are designated as ordinates, 
and numbered consecutively 1, 2, 3, 4, &c, beginning with 
the one nearest to the clearance line. It is immaterial whether 
the spacing comes out even with the end of the diagram ; but 
in cases where they do not, it is only necessary to make an ad- 
ditional spacing that will extend beyond the length of the dia- 
gram, (as shown in Fig. 55), and treat it the same as the other 
points. Now in order to utilize the properties of the hyperbola 
in laying out the theoretical curve, it will be necessary to draw 
short lines cutting the ordinates at the proper height, meas- 
ured vertically from the vacuum line ; so that if the pressure at 
any ordinate, be multiplied by the number representing the volume 
of the same ordinate, the product will always be the same, at 

LOFC. 



IOO Steam Engine Indicator 

whatever point selected ; for example : Suppose on being meas- 
ured by the scale of the diagram, (No. 80) the height of the 
point of cut-off C, from the vacuum line V, be found to show 
an absolute pressure of 100 pounds per square inch ; with a vol- 
ume equal to three of the divisions, into which the diagram has 
been divided. Then 100 pounds multiplied by 3, equals 300; 
which will be our constant number, to be divided for all other 
pressures or volumes. Consequently the height at which the hy- 
perbola will cut any desired ordinate, may be found by dividing 
the constant 300, by the number of the ordinate; that is the 
height of ordinate 4, is found by dividing 300-^4=75, and in 
the same manner the height of ordinate 5 is found by 300-f- 5 = 
60, or 300-=- 6= 50, &c, which will be the heights to be set off 
in divisions of the scale (each division representing pounds 
pressure), at the different ordinates. If so desired, the con 
struction of the curve may be commenced either at the termi- 
nal pressure, or just before the point of release, and points lo- 
cated on the ordinates, in the opposite direction by the same 
method. In this case the terminal shows an absolute pressure 
of 25 pounds, per square inch; and having a volume of 12 di- 
visions; therefore 25 X 12 — 300, which if divided by the num- 
ber representing any other volume or ordinate, we have the 
same results for pressure as by the first method. Instead of 
using the height of the lines to represent pressure, they may 
just as well be considered to represent inches, and fractions of 
an inch, as follows : the vertical height of the point of cut-off 
C, from the zero line V, being 1% inches, and on ordinate 3, 
therefore 3X 1^ = 3.75 inches, which is our constant number 
by this method. Hence 3. 75-^-5 = . 75 of an inch, which will 
be the height of the point above the vacuum line, on ordinate 
5, through which the curve will pass, and the heights of all 
other points may be found, by dividing the constant 3.75 inches, 
by the number representing each ordinate. The heights of all 
points must be measured from the vacuum line. 



A nd Its Appliances. 



IOI 



The location of the vacuum line may also be ascertained 
by dividing the pressure of the atmosphere, 14.7 pounds, by 
the scale of the spring-, and the quotient will be in inches ; for 
example: 14.7-^80— . 183 of an inch below the atmospher- 
ic line. This method of constructing the hyperbola, or isother- 
mal curve, as represented in Fig. 55, is intended to show more 
particularly, the principle upon which the curve is projected, 
rather than to lay any claim to simplicity. There are various 
geometrical methods, much more preferable, for projecting the 
theoretical curve ; all of which give about the same results, as 
the one described. 

One simple and convenient plan of doing it, is represented 




Fig. 56. 
in Fig. 56, and is as follows: Draw the vacuum line V, Vi, 
parallel with the atmospheric line H, I ; at a distance below it 
representing 14.7 pounds, by the scale of the diagram; also 
draw A, E, parallel to the atmospheric line to represent the 
boiler pressure, erect the clearance line K, at a distance from 
the end of the diagram, that will represent the percentage of 
clearance in the engine ; said line being perpendicular to and 
cutting the vacuum line at V. Select any point on the actual 
curve, before commencement of the exhaust; as at B, and from 
that point draw a vertical line, cutting A, E, at E. From E, 



102 Steam Engine Indicator 

draw the diagonal E, V, and from B, draw a line parallel with 
the atmospheric line, intersecting the diagonal E, V, at D. 
From this intersection at D, erect a perpendicular cutting A, 
E, at the point C. Then C will be the theoretical point of cut- 
off, and D, C, is called the cut off line. From C, mark off any 
desired number of points on A, E, as i, 2, 3, 4, &c, and draw 
a perpendicular from each toward the atmospheric line; also, 
from the same points, draw diagonals to the vacuum point V. 
At the intersection of the diagonals with the cut-off line D, E, 
draw horizontal lines to meet the perpendiculars from 1, 2, 3, 
4, &c, and the intersection of these lines are the points 
through which the theoretical curve must pass. This method, 
(as well as all others), of constructing the hyperbolic curve is 
based on the assumption that the temperature of the steam, 
(or other medium) remains the same throughout its range of 
movement ; and also that the piston and valves are absolutely 
tight, as well as an absence of condensation, or any other dis- 
turbing influences. 

It is well known in indicator practice, that in taking dia- 
grams from a steam engine cylinder, we are subjected (at times) 
to all of the influences here mentioned. The temperature of 
the steam changes during the stroke, and usually we find the 
piston and valves, more or less leaky ; also initial condensation 
and re-evaporation takes place, (to a certain extent) all combin- 
ing to cause a departure of the actual (more or less) from the 
true theoretical curve. Therefore one of the objects, in con- 
structing the theoretical curve, is for the purpose of comparing 
and ascertaining the extent of this departure, where princi- 
pally located ; to study and find the cause of any discrepancies, 
so as to enable the engineer to apply the necessary means to 
correct, as nearly as possible, any disagreements that may ap- 
pear in the actual curve. 

In the construction of the theoretical curve, it has been 
assumed that the temperature of the steam remains the same 



A nd Its Appliances . 103 

throughout the stroke ; whereas the temperature of the steam 
in an engine cylinder, gradually decreases from point of cut-off 
to the end of expansion. Hence, (all other conditions being 
perfect) temperature alone would result in a slight disagreement, 
and cause the actual curve at its terminal (with a given cut-off) 
to be a little below the theoretical. The re-evaporation of the 
steam condensed in the earlier part of the stroke, however, 
will later on, tend in a measure, to increase the pressure, there- 
by raising the actual expansion line to more nearly conform 
with the theoretical curve ; therefore as a general thing, a 
close approximation of the actual expansion curve, with the 
theoretical, may be taken as evidence of correct valve adjust- 
ment, and good practice. It is always advantageous to draw 
the true theoretical line on the diagram, in order that the ac- 
tual line may be compared with it. 






104 Steam Engine Indicator 



CHAPTER XV. 



ADIABATIC CURVE AND POINT OF CUT-OFF. 



The curve formed in accordance with the principles of the 
Mariotte law, depends for its correctness upon the condition 
that the temperature of the steam in the cylinder remains the 
same during the entire stroke ; and the curve that coincides 
with this law of expansion, is the Hyperbolic or Isothermal, 
in which it is assumed that the steam within a cylinder during 
expansion is of exactly the same temperature throughout the 
length of the diagram ; whereas the pressure from the point 
of cut-off, to the end, is continually changing, and any change 
in the pressure of steam, is always accompanied by a change 
of temperature ; therefore the application of this law to a dia- 
gram from a steam cylinder, would not be absolutely correct, 
because for any change in volume of the steam, the corres- 
ponding change that takes place in pressure, would be more 
than if the temperature had remained constant : or more, than 
of a curve constructed in accordance with the Mariotte law. A 
method of improving this condition of temperature, and pres- 
sure, is by means of a steam jacket surrounding the cylinder, 
for transmitting heat from said jacket to the steam within the 
cylinder during expansion ; and thereby in a measure supply- 
ing the necessary heat for re-evaporation, and also for increas- 
ing the temperature, and consequently the pressure, thereby 
raising the actual line of diagram, in the latter part of the 



And Its Appliances, 



105 



a. a 6, 



stroke and thus causing it to very nearly conform to the Isoth- 
ermal or theoretical curve. 

In case of exposed cylinders, or where no provision is 
made for transmitting heat to the steam during the stroke, a 
curve may be drawn approximately, representing this curve of 
actual conditions; wherein, all changes of volume and tem- 
perature are accompanied by a change of pressure. This curve 
is called the Adiabatic ; as shown in Fig. 57, and may be, in fact, 
considered the true theoretical curve, and more nearly corres- 
ponding to the actual change of pressure that takes place, dur- 
ing expansion in an unjacketed steam cylinder. We are not 

aware of an absolutely 
correct method of con- 
structing the Adiabatic 
curve; which term 
means, that when steam 
or other medium is un- 
der either expansion or 
compression, no heat 
enters or leaves it dur- 
T ing that time. An ap- 
proximate cur^e may 
be drawn with the aid 
Fig. 57. of a table of the prop- 

erties of saturated steam ; although in most cases the consid- 
eration of this curve is more a problem for experts, than for 
the average engineer. 

Diagram Fig. 57, is presented to show the difference be- 
tween the two theoretical curves, as compared with the actual 
line of the diagram. The upper full line T, C, is the adiaba- 
tic, and T, B, shown in dotted lines, is the isothermal curve ; 
while the lower full line T, A, represents the line described 
by the indicator. If the top, (instead of the terminal) of the 
curve T, C, had been made to coincide with the theoretical 
point of cut-off B, the adiabatic would have fallen about two 




106 Steam Engine hidicator 

pounds per square inch below the theoretical curve at the ter- 
minal. 

In almost all diagrams however, from engines having tight 
pistons and valves, with properly jacketed cylinders, and 
wherever a high mean effective pressure, with a low terminal 
is obtained, thereby securing good efficiency and economy ; it 
is found in all such cases that the actual curve produced by the 
indicator, conforms very nearly with the Isothermal or theoret- 
ical curve. The fact of such agreement therefore must be due to 
a transmission of heat to the steam in the cylinder during expan- 
sion ; thus increasing the temperature and thereby producing a 
re-evaporation of apart of the steam condensed in the earlier part 
of the stroke. As the isothermal curve is very easily drawn 
and apparently correct enough for all practical purposes, it is 
therefore the curve now almost universally used by all classes 
of engineers, for the purpose of comparing with it, the lines 
of the actual diagram ; and where any considerable departure 
is found in the actual curve, all efforts are directed toward 
making such changes in the valve, and piston mechanism, as 
may be necessary to produce uniformity and a close coin- 
cidence of the actual line with the isothermal, and where they 
do so agree is generally considered an evidence of correct 
valve adjustment and efficiency of the engine. This presump- 
tion is no doubt nearly correct in most cases, with steam 
jacketed cylinders, and where the piston and valves are tight ; 
but a close agreement- must not always be taken as conclusive 
evidence of economical results ; as we often find in practice 
some actual diagrams that coincide very nearly with the the- 
oretical ; but still upon investigation of the amount of steam 
used in the engine, they will be found to be deceptive and the 
opposite of economical conditions. 

This deception in many cases arises from a leaky condition 
of the piston and valves, rather than from any lack of proper 
adjustment in the timing of these parts ; therefore any 



And Its Appliances. 107 

decided disagreement of the actual curve from isothermal, gen- 
erally indicates a leakage of steam, either through the valves 
or piston or both ; and these may enter into combination, in such 
a manner, as to be very misleading. The consequences of a 
leaky steam valve are that it will always cause the actual 
curve of the diagram to be higher than it should be at the 
terminal from a given cut-off, The actual curve in Fig. 57, 
represents the effect on the diagram of a leaky steam valve. 
In this case the Isothermal (shown in dotted lines), has been 
started at the end of the expansion, for the purpose of showing 
how much more work might have been done by the steam, 
from the given terminal ; whereas if it had been drawn to coin- 
cide at the commencement, with the absolute point of cut-off, 
(that is, at the intersection of the actual curve with the line 
D, B,) it would have shown the expansion line of said curve 
considerably higher than the theoretical at the terminal T ; 
this being due to the extra amount of steam entrained through 
the valve after cut-off and during expansion. 

If, in the present instance the piston had leaked just suf- 
ficient to cause the expansion line to coincide with the theoret- 
ical ; then the diagram might have been considered from obser- 
vation alone; as representing economy and good conditions in 
the engine; when in fact the reverse of this is the case, owing 
to leaky condition of both of the parts named. Therefore in 
order to secure the most economical results in the steam en- 
gine, it is of the first importance, and absolutely necessary 
that the valves and piston, be practically tight, in order that 
all losses arising from this source shall be brought to a mini- 
mum, A leaky steam valve will be less noticeable at the com- 
mencement, or in the earlier part of expansion, because of the 
slight difference of pressure at that part of the stroke, between 
the steam in the cylinder and that in the steam chest, but will 
become more apparent on the expansion line, as these pres- 
sures become more unbalanced in the latter part of the stroke. 



108 Steam Engine Indicator 

Also a leaky piston will be indicated by a sudden falling away 
of the actual curve from the theoretical at the beginning of 
expansion, due to the difference in pressure between the 
opposite sides of the piston, but as the pressures become more 
equalized later in the stroke, this difference will finally dis- 
appear. If the valves and piston are absolutely tight, (thereby 
obviating all leakage) and also, if no re-evaporation takes 
place, then the theoretical curve drawn strictly in accordance 
with the principles of the Mariotte law, must necessarily be, at 
the point of release (from a given cut-off), higher than the ac- 
tual curve, principally on account of the increasing volume of 
the steam, thereby diminishing its heat, and consequently its 
pressure during expansion. But in indicator practice the re- 
verse of this is usually found, and in most cases the actual 
curve will be above the theoretical at the point of exhaust open- 
ing. This evident rise of pressure, in the latter part of the 
stroke, is claimed by some engineers to be due to a re-evapor- 
ation of the steam, that has lost a portion of its heat, and 
therefore condensed, by contact with the colder surface of 
the cylinder at the commencement and earlier part of the 
stroke ; said heat being again restored in the latter part of the 
stroke by transmission from the inner surface of the cylinder. 

It is construed by others to be due, more to defective and 
leaky steam valves than to re-evaporation. It may be due 
either to the latter, or to a leaky steam valve, or both com- 
bined, and therefore becomes a matter for consideration and 
judgment in most cases on the part of the engineer. 

The rise in pressure from re-evaporation alone, would hardly 
cause the actual line to go much, if any, above the theoretical ; 
consequently a close agreement of the actual line of the dia- 
gram to this line, is all that can be expected, or desired under 
the circumstances. 

The location of the correct point of cut-off, on the diagram 
is another matter that requires considerable experience and 



A nd Its Appliances. 



109 



judgment in selecting the best point on the actual curve, to be 
used as a basis, with any of the various geometrical methods of 
construction, employed for locating the correct point of cut-off ; 
all of which give about the same results. 

One method of con- 
struction for locating 
the point, is repre- 
sented in Fig. 58, as 
follows: Draw the 
vacuum line V, Vi, 
parallel and below the 
atmospheric H, I, at 
a distance equal to 
14.7 pounds by the 
scale of the spring. 
Draw the line A, E, 
also parallel and just 
or near the top of the diagram. The clearance 




Fig. 58. 



touching 

being known, or de- 
termined by either of 
the methods previous- 
ly described erect the 
clearance line K, ac- 
cordingly ; select any 
point on the expansion 
line, where it is known 
that the steam and 
exhaust valves are 
closed, as at D, and 
erect a perpendicular, 
intersecting the line 
A, E, at B; from B, 
draw the diagonal 
line to to the vacuum point V, and from D, draw a horizontal 





E 






a a 










1 \l 






1 N v 

1 \ 




'/1 






( 

^- — 


\ 
/ 


V 

\ 1 


Z^- 








X 










-> 



Iri 



nr 



Fig. 59. 



no 



Steam Engine Indicator 



line cutting the diagonal B, V, at F. From F, erect a perpen- 
dicular intersecting the line A, E, at C. ThenC, is the correct 
point of cut-off ; or is where the further admission of steam to 
the cylinder must be stopped, in order that the expansion line 
shall pass through the selected point D. This diagram is rep- 
resented as having been taken from a single cylinder condens- 
ing engine, the steam valve having no apparent leakage, and 
the point D, as being selected bclozv the atmospheric line. 

The diagram represented in Fig. 59, is taken from the 
same style of engine as Fig. 58 and the method of locating the 
point of cut-off is precisely the same. The only difference be- 
tween the diagrams, being in the location of the point selected 
on the expansion line. Here the point D is nearer the center 
of the curve, and above the atmospheric line, and gives the 
correct point of cut-off at C. The construction of the theor- 
etical curve on the diagram, in this case, indicates a consider- 
able leak in the steam valve. It is not necessary that the line 

A, E, be drawn at the 
extreme top, as in dia- 
grams where the valve 
is slow in closing, and 
thereby causing the 
curve of cut-off to be de- 
cidedly rounded, it may 
be better to draw the 
line through the abso- 
lute closure, as near as 
•can be observed ; in or- 
der that the contrast 
may be more plain at 
Fig. 60. that point. 

Another very simple method of. locating the point of cut- 
off , is represented in Fig. 60, and is as follows : Draw the 
vacuum and clearance lines the same as in the preceding 




And Its Appliances, I f / 

figures ; also the line A, E, near the top, or through the noted 
point of cut-off. From V, draw the diagonal line at an angle 
of 45 degrees, with the vacuum line, and intersecting the line 
A, E, at B, drop a line from B, cutting the expansion line at 
D. Place one point of a pair of dividers at B, and with a 
radius equal to B, D, describe the arc D, C, cutting A, E, at 
C, then C will be the correct cut-off point. The drawing of 
the diagonal line will be more quickly done by the use of a 45 
degree triangle, but in the absence of one, may be done by 
the method as shown in Fig. 60. Place one point of the divid- 
ers at V, and with any convenient radius describe the arc 1,2; 
then with the same radius, and from 1 and 2, draw short arcs, 
cutting each other at the point 3. From V, draw the diagonal 
through the intersection at 3, which will be the desired angle. 






\ i2 Steam Engine Indicator 



CHAPTER XVI 



THE FOOT-POUND, AND MEASUREMENT OF DIAGRAMS. 



The foot pound is the unit of measurement in computing 
the power of steam engines and represents the work required 
to lift one pound, one foot high. The established standard of 
horse-power being 33,000 foot pounds or an equivalent amount 
of work, such as 1000 pounds lifted 33 feet; 500 pounds 66 
feet; or 100 pounds lifted 330 feet in one minute. The horse 
power of a steam engine is therefore denoted by the number 
of pounds it is capable of raising to a given height in one min- 
ute. The usual and correct method of computing this is by 
multiplying the area of the piston (in square inches), by the 
mean effective pressure of the steam acting against the piston 
throughout the stroke, and also by the speed of the piston 
(in feet), per minute, and dividing the product of such multi- 
plication by 33,000, the quotient will be the indicated horse- 
power. 

For instance : Suppose we have an engine in which the 
piston area is 201 square inches, with a mean effective pressure 
of 30 pounds per square inch, and a piston speed of 450 feet 

per minute, then — = 82.22+ indicated horse-power. 

33,000 

The actual efficient horse-power will be somewhat less; de- 
pending upon the amount of friction in the engine. A ready 
and convenient method of calculating the horse-power from a 



A nd Its Appliances. 113 

number of cards from the same engine, is for the engineer to 
first compute the horse-power of his engine at one pound mean 
effective pressure and using the number so found as a constant 
or multiplier for all other mean effective pressures. For illus- 
tration : Suppose as in the preceding example, the piston area 
to be 201 square inches, and piston speed 450 feet per minute, 

then - — ^- = 2.74+ which is the horse-power of the engine 
33,000 

at one pound mean effective pressure, and which may be used 
as a multiplier for all other mean effective pressures in the en- 
gine ; the product of the multiplication will be the total 
indicated horse-power. Hence the horse-power of the engine 
at one pound mean effective pressure as above being 2.74+ 
therefore at 30 pounds it will be 30x2.74=82.20, or at 25 
pounds mean effective pressure would be 25 X 2.74=68.50 in- 
dicated horse-power. The factors connected with the subject 
are therefore, as before stated. 1st. The area of the piston 
(in square inches), which can be obtained from a table of the 
diameters and areas of circles, or may be computed by multi- 
plying the square of the diameter in inches by the decimal 
.7854; the product will be in square inches. 2nd. The speed 
of the piston (in feet), per minute and which may be found by 
multiplying twice the length of the stroke (in feet), by the 
number of revolutions of the crank, which will give the piston 
speed in feet per minute. 3rd. The force or mean effective 
pressure of the steam, acting upon the piston during the time. 
The product of all three being divided by 33,000, the standard 
unit of horse-power. 

The indicator in most cases is used principally for deter- 
mining the horse-power ; but by the aid of its record made on 
the card, the impelling force against the piston at all periods 
of the stroke, is made visible, and thereby furnishes an index 
of the work performed, and enables the engineer to study in- 
telligently many other important matters connected with the 



H4 



Steam Engine Indicator 



S/idlt. ra. 



problem of steam economy. In order to determine the horse- 
power of an engine, it first becomes necessary to ascertain from 
the diagram, the mean effective pressure of the steam acting 
upon the piston during the stroke of the engine. The finding 
of the mean effective pressure is rapidly and easily accom- 
plished by the use of the Planimeter, an instrument especially 
adapted for the purpose ; but when an instrument of this kind 
is not at hand, this pressure may be approximately determined 
by means of a number of lines drawn through the diagram as 

represented in Fig. 61, 
and is as follows : Di- 
vide the diagram into 
any number of equal 
parts, and draw lines 
(called ordinates), 
through each division 
and perpendicular to 
the atmospheric line ; 
thus dividing the dia- 
gram into a number of 
small areas. The mean 
effective pressure may 
now be found by meas- 
uring the height of 
each line, in pounds, by a scale corresponding with the scale of 
the spring with which the diagram was taken ; then by adding 
the pressures so found at each division and dividing their com- 
bined sum by the number of divisions into which the diagram 
has been divided, will give the mean effective pressure in 
pounds per square inch. The diagram, Fig. 61, is shown (by 
the ordinates in full line), to be divided into ten equal parts; 
consequently ten would be the divisor for the combined sum 
of the ordinates in this case ; for example : The combined 
length of the ordinates measured in pounds by the scale of the 




Fig. 61. 



A nd Its Appliances. 115 

spring (50) is 428 and this divided by the number of divisions 
as 428-f- 10=42.8 pounds mean effective pressure. 

Where greater accuracy is desired, or where the outlines 
of the diagram are very irregular, it may be advisable to sub- 
divide as shown in dotted lines, making twenty divisions, and 
consequently dividing their combined sum by twenty. In dia- 
grams where this irregularity exists only in a part of its 
length, it is sufficient (at that part alone), to sub-divide on each 
side of the line or lines, for which the pressure is required; 
and measure the pressure on each sub-division ; add together 
and divide their sum by two (2) ; the quotient will be the pres- 
sure sought on the full division line as shown at the top of the 
diagram in Fig. 61. 

In place of measuring the heights of the ordinates, (in 
pounds) by the scale of the spring, each may just as well be 
measured in inches. If the sum of their combined length be 
multiplied by the scale of the spring, and divided by the num- 
ber of ordinates, the quotient will be the mean effective pres- 
sure in pounds per square inch, acting against the piston 
throughout the stroke. For example : The combined length of 
the ordinates measured in inches is 8.56, then 8. 56X 50^ 10= 
42.8 pounds mean effective pressure, the same as before. An- 
other convenient method, which has the merit of simplicity 
may be staten as follows : If we draw the number of ordinates 
in the length of the diagram equal to the number correspond- 
ing with the denomination of the spring, then the combined 
length of the ordinates in inches will be the mean effective 
pressure in pounds per square inch. For example : Suppose in 
the diagram, Fig. 61, the spring to be a 50 and that the length 
of the diagram be divided into the same number (50) of equal 
parts, then each inch of the combined length of the ordinates 
would represent one pound mean effective pressure. If it had 
been divided into twenty-five (25) parts, then each inch would 
represent two (2) pounds mean effective pressure, etc., and in 



Ii6 Steam Engine Indicator 

any case by dividing the number representing the denomina- 
tion of the spring by the number of division in the length of the 
diagram ; the quotient will be the multiplier for the combined 
length of the ordinates in incites, and the product of such mul. 
tiplication will be in pounds mean effective pressure. For in- 
stance : The combined length of the ten divisions in the dia- 
gram, Fig. 61, is 8.56 inches, and the scale of the spring is 50, 
therefore 50-^-10=5 and 8. 56X 5 = 42.8 pounds mean effective 
pressure, the result being precisely the same as by the other 
methods. In working out the diagrams it is advisable to make 
the divisions as numerous as convenient, which tends to more 
accurate results, and particularly so where the outline of the 
diagram is very irregular. 

In cases where a scale of the spring is not at hand, a con- 
venient method of finding the combined length of the ordinates 
is by taking a narrow strip of paper and marking on it the 
height of each division, commencing at No. 1. Mark its 
length on the paper, then place the mark made at the top of 
No. 1 on the bottom of No. 2 and mark the top of No. 2, and 
so on successively to the end of the diagram, then measuring 
their total combined length in inches which being multiplied by 
the number of spring, and divided by the number of divisions, 
will give the mean effective pressure, in pounds, per square 
inch, or, in place of measuring with a strip of paper, it may be 
as correctly done by drawing a straight line of sufficient length 
to contain the combined length of the ordinates, and with a 
pair of dividers set to the length of each different ordinate suc- 
cessively; commencing at No. 1, and transferring the length 
of each upon the line. The mean effective pressure may then be 
found from the total length in inches after all the measurements 
of the ordinates have been transferred to the line, by either of 
the two latter methods of computation. 

The diagram, Fig. 62, represents the effect in a non-con- 
densing engine of cutting off the steam at a very early part of 



And Its Appliances. 



117 




-*^r 



the stroke, and shows the expansion line crossing and running 
below the atmospheric line for the greater part of the stroke. 
This result is a general thing brought about in diagrams from 
an engine having insufficient load. In this case the diagram 
is composed of two distinct parts, and must be treated as such 
in computing the horse-power of the engine. 

In Fig. 62, all ordi- 
nates above the atmos- 
pheric line, and to the 
left of where the expan- 
sion crosses the back 
pressure line, will rep- 
resent positive pressure, 
and all ordinates to the 
right of the above, and 
between the back pres- 
sure and boundary 
line of the diagram, 

p- will be negative, and 

Fig. 62. the combined length 

of the latter must be deducted from the former, in order to as- 
certain the mean effective pressure. For example : Suppose 
the scale of the spring to be 40, and the combined length of 
the ordinates of positive pressure to be 4.05 inches while the 
combined length of the lines of negative pressure is 1.65 
inches, then the difference will be 4.05—1.65 = 2.4 inches. 
The number of divisions of the diagram (20) being just one- 
half of the scale of the spring (40), it is only necessary to mul- 
tiply the difference in the length of the lines by two ; that is 
2.4X2 = 4.8 pounds mean effective pressure throughout the 
stroke. An indicator diagram like Fig. 62 always indicates a 
loss of efficiency and measures should at once be taken to rem- 
edy the evil. 

In the matter of the computation of diagrams for mean 
effective pressure alone, it may here be well to state, that 



^ujomii/ 



1 1 8 Steam Engine Indicator 

neither the atmospheric, vacuum, or clearance lines become 
factors in the case ; therefore, we have only to deal with the 
lengths of ordinates within the actual boundary line of the 
diagram. 



A i i* 






And Its Appliances. 11 9 



CHAPTER XVII. 



EXPANSION OF STEAM. 



The expansion of steam in the cylinder of an engine per- 
forming work coincides very nearly with the principle of the 
law pertaining to gases, and known as the Mariotte law ; (as 
before noted in Chapter XIV) wherein the pressure varies in- 
versely as the volume ; the temperature remaining the same. 

Upon opening communication (at any observed pressure 
of steam) between a boiler, and the cylinder of a steam engine, 
a corresponding pressure of steam will be exerted against the 
piston, and unless the steam be either condensed, or discharged 
from the cylinder, the same pressure will continue to act upon 
the piston ; even after the valve has been closed that commun- 
icates with the boiler, and this pressure will continue so long 
as the volume and temperature remains unchanged. 

If steam is supplied from a boiler to move a piston altern- 
ately in a cylinder, and the valve for admission of steam re- 
mains open during the full stroke of the piston, then the 
cylinder will be filled with steam at each stroke of the piston, 
of a pressure nearly equal to that of the boiler ; and is conse- 
quently exhausted also at nearly the same density. 

The parallelogram or rectangle shown in dotted lines b, 
d, vi, v, of Fig. 63 represents a theoretical indicator diagram 
from a condensing engine under such conditions; the line 



120 



Steam Engine Indicator 



v, vi being the line of absolute vacuum, and b, d, the boiler 
pressure. 

Assume an indicator to be attached to the cylinder of such 
an engine, and the drum carrying the paper be given a recip- 
rocating motion to coincide (on a reduced scale) with the mo- 
tion of the engine piston ; then if before admitting steam to 
the indicator piston, (and while the drum is in motion,) the 



if 








"^" 




1 

1 
1 














1 

1 








X 


X 




F |\ 










CtJ 

























, 


U/ 



Fig. 63. 

indicator pencil be brought in contact, with the drum, a hori- 
zontal line a, ai, (called the atmospheric- line) will be traced 
upon the paper; in length, proportioned to the stroke of the 
engine piston ; and also during this time, the pressure of the 
atmospheric will have free access to both sides of the indicator 
piston. 

If communication be now suddenly opened between the 
steam cylinder, and indicator, at a time when the pencil is at 
the point a, the pencil will ascend, and trace upon the paper 



And Its Appliances. 12 1 

the vertical line a, b, to a certain height, depending upon the 
pressure of the steam, and also upon the strength or scale of 
the indicator spring in use ; and this height will represent the 
pressure per. square inch of the steam within the engine 
cylinder. 

Assuming now that the engine piston had just commenced 
to move from left to right, and the admission of steam, con- 
tinues until the completion of the stroke ; the pencil will have 
traced the line b, d, representing in this case the mean pres- 
sure of the steam throughout the stroke. 

If at the point d, the valve for the admission of steam be 
closed, and this volume of steam be suddenly condensed by 
being exhausted into the condenser, (thereby creating a vac- 
uum) the pencil will descend, and trace the line d, vi, and 
consequently on the return stroke follow along the line vi, v, 
to the commencement; thus describing a parallelogram of 
which the horizontal line V, VI, would represent the length of 
the stroke of the piston, and the vertical line v, b, would rep- 
resent the total steam pressure in pounds per sqaure inch act- 
ing upon the piston ; therefore the area of this parallelogram 
would represent pounds pressure, multiplied by the distance in 
feet moved through by the piston in a single stroke. 

The theoretical diagram here described is one that never 
occurs absolutely- in indicator practice ; for the reason that the 
varying circumstances arising in the use of steam, would always 
preclude the possibility of obtaining such a result ; therefore it is 
only drawn for the purpose of making a comparison of effi- 
ciency, between it, and the actual diagram, taken as near as 
possible under the same conditions. 

In the foregoing, steam is supposed to be admitted to the 
cylinder, during the entire length of stroke of the piston; 
without any attempt to employ and utilize the benefits to be 
derived from the expansive properties of the steam. 



122 



Steam Engine Indicator 



The diagram in full line of the same figure, show approxi- 
mately the outline of an actual diagram, (in practice) as the re- 
sult of such an adjustment of valves, (as herein described) as 
would admit steam at one end, and exhaust at the other, alter- 
nately during the entire length of each stroke of the piston. 

It will be observed that the actual diagram may deviate to 
a considerable extent, from the theoretical, in accordance with 
various circumstances. 




It t A. J 4 ? <* J 

Fig. 64. 

For instance, the boiler pressure may not be fully real- 
ized ; also the interval of time that must elapse between the 
point of commencement of opening, or closing of the valves, 
and the absolute accomplishment of the same, will produce a 
wire drawing effect of the steam, and will invariably cause the 
corners of the diagram to be, more or less, rounded off, as 
shown in the diagram. 

The location of the line representing the back pressure on 
the return stroke, will depend upon the degree of vacuum 



And Its Appliances. 123 

maintained in the condenser, and this will usually be found in 
most diagrams, to be from three to five pounds above the line 
v, vi, of absolute vacuum. 

The production of diagrams like the one shown in Fig. 63 
are only not desirable, but the reverse of economical, and 
such results can only be entertained where the desire is to ob- 
tain the greatest possible power, from a given size of engine, 
without regard to the highest economy. 

In order to save steam, or to better realize the econ- 
omy, and efficiency of a given amount of steam to a 
greater degree, its admission to the cylinder must be stop- 
ped, or cut-off after the piston has moved only a portion of 
the stroke ; and as the piston continues to move along the 
cylinder (thereby increasing the volume of the steam so con- 
fined and allowing it to act expansively), its pressure from the 
point of cut-off will gradually diminish to the end of the 
stroke, and in such proportion as corresponds to its increased 
volume. 

Suppose we have a boiler under a steam pressure of 60 
pounds per square inch, to which we add the pressure of the 
atmosphere (say 15 pounds), making a total of 60+15 = 75 
pounds per square inch absolute pressure. 

Now if this steam be admitted to the cylinder of an engine, 
and the admission stopped after the piston had traveled one- 
half of its length of stroke, as represented by b, c, Fig. 64, it 
will have performed a certain amount of work, which may be 
represented in foot-pounds; the amount being the product of 
the total pressure in pounds acting upon the piston, multi- 
plied by the distance in feet it has passed over. 

If this steam, before being discharged from the cylinder is 
allowed to expand to double its volume, thereby forcing the 
piston to the end of the stroke, an additional amount of work 
will have been performed with this same amount of steam, and 



124 Steam Engine I e die at or 

result in effecting a decided economy in the engine ; as this 
excess of work has been obtained through utilizing the expan- 
sion of the steam. 

In this case the steam was expanded to twice its volume at 
the termination of the stroke of the piston, with a pressure of 
ljy 2 pounds per square inch, or just one-half what it was at 
half stroke. 

In Fig. 64, suppose the stroke of the piston to be 4 feet 
and this length divided into eight equal parts, 1, 2, 3, etc., 
each part or volume representing six inches, or one-half foot 
of the stroke ; then if the piston be acted upon by an absolute 
pressure of steam (as before stated), of 75 pounds per square 
inch at the beginning, and continued to the fourth division, 
(as at c), equal to one-half of the stroke, it will have performed 
an amount of work which may be represented by the mean 
pressure (75 pounds) multiplied by 4, (75X4)=300 foot pounds 
of work for each square inch of the area of the piston. 

If the admission of steam be stopped or cut-off, after the 
piston has arrived at half stroke, this volume of steam in the 
cylinder will expand ; and its pressure will gradually diminish 
to the end of the stroke ; and the indicator pencil will trace 
the curve line c, g, and when the exhaust valve opens (assum- 
ing for the time a perfect vacuum in the condenser), it will de- 
scend to the point vi. 

In the diagram, Fig. 64, there is only one-half as much 
steam admitted into the cylinder during the stroke, as in the 
case of diagram Fig. 63, but it will be readily observed by a 
comparison of the diagrams, that the area of the former is 
greatly in excess of half that of Fig. 63, in fact, by actual com- 
putation, (the rule for which will appear later on) its area will 
be found to be about .846 of that of Fig. 63, and with a 
mean pressure of 63.49 pounds per square inch during the en- 
tire stroke ; (eight divisions) therefore the work done by the 
steam in the first-half of the stroke being represented by 



And Its Appliances. 



125 



75X4=300, the amount during the whole stroke will be 

1 507. Q2 — soo 207.02 - . , 

63.49X8=507.02, hence — =z — y =.003, equivalent 

300 300 

to a gain of power of about 69.3 per cent. 

This has been obtained through utilizing the expansion of 

half the quantity of steam that would be employed during the 

stroke of an engine represented by the theoretical diagram 

Fig. 63. 

6- 




7 



4 r t 

Fig. 65. 

Fig. 65 is a further illustration of a diagram in which the 
admission of steam is cut off at one-fourth, and expanded 
the balance of the stroke. 

In this case the amount of steam used is only one-fourth 
of that at full stroke, but the total area of the diagram is over 
.58 of the full theoretical diagram; and which is equal to a 
mean pressure of 44.74 pounds per square inch throughout the 
entire stroke, (the total initial pressure as stated being 75 
pounds per square inch.) 



126 Steam Engine Indicator 



Consequently the work done during the first quarter (one- 
fourth) of the stroke is represented by 75 X 2= 150, and during 

2 C 7 Q2 — 1^0 

the entire stroke by 44.74X8=357.92, therefore 

207 Q2 

— (-1^-= 1.38 equivalent to a gain of 138. per cent 

In making calculations for pressure of steam after it has 
been expanded, it is the total pressure that must be considered, 
and which is reckoned from absolute vacuum. 

Consequently the extra amount of force thus obtained, and 
utilized in impelling the piston the balance of the stroke, may 
be considered theoretically as just so much gain, over the single 
effect of the same amount of steam ; as none of this additional 
pressure would have been realized upon the piston, if the 
stroke had terminated at the point where the steam was cut-off. 

From this theoretical gain however, there are certain 
losses that must be deducted ; such as friction of the engine 
during expansion ; the loss of temperature caused by the grad- 
ual reduction of pressure of the expanding steam ; and this 
loss is further increased by the abstraction of heat from the 
cylinder during the return stroke ; thereby producing a com- 
paratively cooling effect on the interior walls of the cylinder 
and also the piston. 

This, as a consequence, necessitates a greater condensation 
of the steam, (in the earlier part of the following stroke) be- 
fore the temperature of the cylinder is again restored to that 
of the entering or initial steam. 

In practice these losses prevent the full theoretical economy 
that might be obtained ; therefore in order that the maximum 
gain from expansion may be realized, they must be reduced to 
a minimum. 

The usual means employed for their prevention, is by 
some system of cylinder covering or jacketing, also superheat- 
ing- ; to obviate the matter of condensation ; this also in 



And Its Appliances. 127 

connection with the best methods of reducing the friction to a 
minimum. 

The economy that may be derived from the expansion of 
steam, when used under different conditions, is an impor- 
tant consideration, and requires ability and good judgment (of 
the engineer) in arriving at the best means for realizing all 
expected or desired results. 

The greatest gain from expansion is generally secured 
in Condensing Engines, but the application of a condenser 
however should be judiciously made, as with loads already too 
light, it would be of little value, and the results disappointing. 






128 Steam Engine Indicator 



CHAPTER XVIII 



HYPERBOLIC LOGARITHMS. 



In the absence of an indicator, the Mean Effective Pres- 
sure of the expanding steam in a cylinder, and the power of 
the engine from a given pressure of steam, and point of cut-off 
may be approximately ascertained, and the average pressure 
per square inch that will be exerted against the engine piston, 
during the stroke can be estimated, by means of the table No. 
i, of Hyperbolic Logarithms; which are calculated for expan- 
sion according to the Mariotte law. 

The Hyperbolic Logarithm as found in the table, is the 
product of the common logarithm multiplied by 2.302585 ; and 
conversely the common logarithm is the product of the hyper- 
bolic logarithm multiplied by 0.43429448. 

The table referred to, contains the hyperbolic logarithm of 
numbers up to 39, which are considered sufficient for applica- 
tion to steam expansion. 

The rule, and method of calculating the Mean Pressure by 
the use of the table is as follows : 

Rule. To the total length of the stroke of the engine pis- 
ton, (in inches) add the clearance in the cylinder at one end 
(also in inches) divide this sum by the length of the stroke at 
which the steam is cut-off, added to the same clearance ; and the 
quotient will express the ratio or number of expansions. 



And Its Appliances. 



129 



Find in the table the logarithm of whatever number is 
nearest to that of the quotient, to which add 1. 

The sum is the ratio of the gain. 

Multiply the ratio thus obtained by the absolute pressure 
of steam, as it enters the cylinder, and divide the product by the 
relative expansion ; the quotient is the mean pressure required. 



No. 


Loga- 


No. 


Loga- 


No. 


Loga- 


No. 


Loga- 


rithms. 


rithms. | 


rithms. 


rithms. 


0.0 


0.00000 


4.0 


1.38629 


7.0 


1.94591 


10 


2.30258 


• 1.1 


0.0.)530 


4.1 


1.41096 


7.1 


1.96006 


11 


2.39589 


1.2 


0.18213 


4.2 


1.43505 


7.2 


1.97406 


12 


2.48491 


1.3 


0.26234 


43 


1.45859 


7.3 


1.98787 


13 


2.56494 


1.4 


0.33646 


4.4 


1.48161 


7.4 


2.00149 


14 


2.63906 


1.5 


0.40505 


4.5 


1.50408 


7.5 


2.01490 


15 


2.70805 


1.6 


0.46998 


4.6 


1.52603 


7.6 


2.02816 


16 


2.77259 


1.7 


0.53063 


4.7 


1.54753 


7.7 


2.04115 


17 


2.83321 


1.8 


0.58776 


48 


1.56859 


7.8 


2.05415 


18 


2.89037 


1.9 


0.64181 


4.9 


1.58922 


7.9 


2.06690 


19 


2.94444 


2.0 


0.69315 


5.0 


. 1.60944 


8.0 


2.07944 


20 


2.99573 


2.1 


0.74190 


5.1 


1 62922 


8.1 


2.09190 


21 


3.04452 


2.2 


0.78843 


5.2 


1.64865 


8.2 


2.10418 


22 


3.09104 


2.3 


0.83287 


5.3 


1.66770 


8.3 


2.11632 


23 


3.13549 


2.4 


0.87544 


5.4 


1.68633 


8.4 


2.12830 


24 


3.17805 


2.5 


0.91629 


5.5 


1.70475 


8.5 


2.14007 


25 


3.21888 


2.6 


0.95548 


5.6 


1.72276 


8.6 


2.15082 


26 


3.25810 


2.7 


0.99323 


5.7 


1.74046 


8.7 


2.16338 


27 


3.29584 


2.8 


1.02962 


5.8 


1.75785 


8.8 


2.17482 


28 


3.33220 


2.9 


1.06473 


5.9 


1.77495 


8.9 


2.18615 


29 


3.36730 


3.0 


1.09861 


6.0 


1.79175 


9.0 


2.19722 


30 


3.40120 


3.1 


1.13140 


6.1 


1.80827 


9.1 


2.20837 


31 


3.43399 


3.2 


1.16314 


6.2 


1.82545 


9.2 


2.21932 


32 


3.46574 


3.3 


1.19594 


6.3 


1.84055 


9.3 


2.23014 


33 


3.49651 


3.4 


1.22373 


6.4 


1.85629 


9.4 


2.24085 


34 


3.52636 


3.5 


1.25276 


6.5 


1.87180 


9.5 


2.25129 


35 


3.55535 


3.6 


1 28090 


6.6 


1.88658 


'9.6 


2.26191 


36 


3.58352 


3.7 


1.30834 


6.7 


1.90218 


9.7 


2.27228 


37 


3.61092 


3.8 


1.33046 


6.8 


1.91689 


9.8 


2.28255 


38 


3.63759 


3.9 


1.36099 


6.9 


1.93149 


9.9 


2.29171 


39 


3.66356 



Table No. 1. 



For example. Suppose steam of 100 pounds absolute pres- 
sure per square inch, be admitted to the cylinder of an engine, 
at the beginning of the stroke (ignoring clearance for the 



130 Steam Engine Indicator 

present), and admission stopped after one-fifth (1-5) of the 
stroke had been completed, and the steam allowed to gradually 
expand to the end of the stroke. 

Then in accordance with the principle of the law, in ref- 
erence to the expansion of gases, the volume of steam in this 
case, on being continually increased, will consequently suffer 
a corresponding reduction in pressure. 

At 2-5 of the stroke the volume will be double, and the 
pressure reduced to x / 2 of the initial, or to 50 pounds per square 
inch; at 3-5 to ^ or 33^ pounds; at 4-5 to ^ or 25 pounds, 
and at 5-5 or the whole stroke the volume is increased 5 times, 
with a reduction of pressure of 1-5 initial or to 20 pounds pres- 
sure per square inch at the termination of the stroke. 

Now what we desire to ascertain in such a case, is the 
average pressure during the entire stroke or, what pressure 
acting uniformally throughout the stroke will perform an 
equivalent amount of work. 

This may be calculated very readily by the use of the 
Table No. 1, in connection with the Rule. Suppose in the 
foregoing example, the stroke of the piston to be 60 inches, 
and the admission of steam be stopped after the piston had ad- 
vanced 12 inches and expansion continuing to the end of the 
stroke; then by the Rule |f = 5 the ratio of expansion. 

This ratio of expansion (5) will be found in the table No. 
1, under the head of numbers, and directly opposite (to the 
right) will be found its hyperbolic logarithm 1.609, to which 
add 1. the sum of which i.-f- 1.609=2.609 the ratio of gain. 

Multiply 2.609 by the initial pressure of steam entering 
the cylinder, and divide the product by (5) the ratio of expan- 
sion : hence -- — - =52.18 which represents in pounds per 

square inch, the average or Mean Pressure that would be ex- 
erted uniformally against the piston during the entire stroke of 
the engine. If the stroke of the engine piston in the above 



And Its Appliances. 1 3 1 

example had been 48 inches, the steam cut-off, after the piston 
had advanced 12 inches, and the absolute initial pressure of 
the entering steam be 80 pounds per square inch, then f|= : 4 
equal the ratio of expansion; the logarithm of which is 1.386 
and represents the ratio of the gain. 

-j 1. + 1.386X80 2.386x80 

Hence — - — — — =47.72 which would ex- 

4 4 

press the Mean Pressure in pounds per square inch impelling 

the engine piston during the entire stroke. 

In computing the above examples for the Mean Pressure, 
the effect of the clearance in the cylinder, has been purposely 
neglected, in order that the calculation might be presented in 
a more simple manner. 

In the case of the latter example, suppose the percentage 
of clearance to have been such as to add two (2) inches in 
length to each end of the cylinder; then 48+2=50 inches, the 
length of stroke with the clearance at one end added ; and by 
adding the same clearance to the distance of cut-off, 12 + 2= 14 
inches, therefore ^=3.57 the ratio of expansion in this case. 

From the table No. 1, we find the nearest number to this 
ratio of expansion is 3.55 the logarithm of which is 1.267 to 

2 267 X 80 
which add 1. then 1.+ 1.267 = 2.267 and — — =50.80 which 

3-57 
represents the Mean Pressure per square inch, when computed 
with the clearance included, instead of 47.72 as before; an in- 
crease of 3.08 pounds per square inch. 

As all calculations of this kind are generally made for ap- 
proximate results or comparisons only, it is in most cases un- 
necessary to take the clearance into consideration, unless it 
should be unusually large, or unless the cut-off should take 
place very early in the stroke; either of which, or both com- 
bined would in a measure cause a variation in the final re- 
sults. 



132 



Steam Engine Indicator 



This indifference, relative to the clearance in the calcula- 
tions proceeds from the fact that the full boiler pressure is 
never fully realized in the cylinder ; and also on account of a 
falling of pressure that often takes place in the cylinder before 
cut-off ; and it may be assumed that what will be gained by 
clearance, is about offset by the failure of the steam to fulfill the 
conditions required. 



Portion of stroke 

at which 
steam is cut off. 


Grade or 

ratio of 

expansion 


Hyperbolic 
logarithm 


Mean pres- 
sure of steam 

during the 
whole stroke 


Percentage 

of gain in 

fuel or power 


1 


9 


X 


V 


% 


To, or 0.1 


10.0 


2.302 


3.302 


230.0 


i , or 0.125 


8.0 


2.079 


3.079 


208.0 


I, or 0.166 


6.0 


1.791 


2.791 


179.0 


tV, or 0.2 


5.0 


1.609 


2.609 


161.0 


1 , or 0.25 


4.0 


1.386 


2.386 


139.0 


To, or 0.3 


3.33 


1.203 


2.203 


120.0 


J , or 0.333 


3.0 


1.099 


2.099 


110.0 


| , or 0.375 


2.66 


0.978 


1.978 


97.8 


T 4 o, or 0.4 


2.5 


0.916 


1.916 


91.6 


J, or 0.5 


2.0 


0.693 


1.693 


69.3 


T 6 o> or 0.6 


1.666 


0.507 


1.507 


50.7 


f , or 0.625 


1.6 


0.47 


1.47 


47.0 


|, or 0.666 


1.5 


0.405 


1.405 


40.5 


T \> or 0.7 


1.42 


0.351 


1.351 


35.1 


f , or 0.75 


1.33 


0.285 


1.285 


22.3 


T 8 o> or 0.8 


1.25 


0.223 


1.223 


20.5 


i , or 0.875 


1.143 


0.131 


1.131 


13.1 


To, or 0.9 


1.11 


0.104 


1.104 


10.4 



Table No. 2. 



It must be understood that the Mean Pressure as estimated 
in the preceeding examples, is the absolute pressure, measured 
from the line of perfect vacuum. 

In non-condensing engines under good conditions, the 
average back pressure will be from one to two pounds above 



A nd Its Appliances. 133 

the atmosphere, or about 16 pounds absolute; and which must 
be deducted from the results obtained. The remainder will be 
the average, or Mean Effective Pressure. 

In condensing engines the back pressure will average from 
about 4^ to 5 pounds irrespective of the atmosphere, being a 
loss through imperfect vacuum ; and which must also be de- 
ducted in this case, in order to obtain the Mean Effective Pres- 
sure. In either case the exact amount of back pressure to be 
deducted will vary ; and such variation will depend mostly up- 
on circumstances, and local conditions. 

The theoretical economy of using steam expansively is 
given in Table No 2, which contains the hyperbolic logarithm 
for numbers running from 10, the grade, or ratio of expansion, 
representing o. 1, or 1- 10 cut-off, to 1.11, representing 0.9, or 
9-10 cut-off, and which may be considered of sufficient range 
for application to the expansion of steam in engines for all 
practical purposes. 

The first column L represents the portion of stroke at 
which steam is cut-off, the second G the grade, or ratio of ex- 
pansion, the third X the hyperbolic logarithm of the number 
or grade of expansion ; the fourth, the mean pressure of steam 
during the whole stroke, and the fifth column the percentage 
of gain in power. 

The per cent of gain by expansion is obtained by multiply- 
ing the logarithm of the number of expansions by 100. 

In the Table no deductions are made for a reduction of 
the temperature of the steam during expansion, nor for any 
loss through back pressure. 

In expansion, the same relative advantages occur, as 
given in the table whatever may be the initial pressure of the 
steam. 

The results, in reference to the percentage of gain as shown 
by the table, is as before stated, theoretical, as from the 



134 



Steam Engine Indicator 



resistance to expansion of the back pressure in a cylinder, and 
from the loss of temperature of the steam by cooling, and also 
from the friction of the steam passages, these results in practice 
are very materially reduced. 

The pressure of the atmosphere is always included in cal- 
culating the expansion ; therefore must be deducted from the 
results in all non-condensing engines. 

CONSTANTS FOR FINDING THE AVERAGE PRESSURE IN THE 
CYLINDER WITH ANY PRESSURE OF STEAM. 



Percentage 




Percentage 




Percentage 




Percentage 




of the 




of the 




of the 




of the 




stroke at 
• which 


Constant. 


stroke at 
which 


Constant. 


stroke at 
which 


Constant. 


stroke at 
which 


Constant. 


Eteam is 




steam is 




steam is 




steam is 




cut off. 




cut off. 




cut off. 




cut off. 




l°/o 


•0560 


21% 


•5377 


41%, 


•7758 


61% 


•9114 


2 


•0982 


22 


5529 


42 


•7841 


62 


•9162 


3 


T321 


23 


•5679 


43 


•7920 


63 


•9200 


4 


•1688 


24 


5823 


44 


•8010 


64 


•9264 


5 


•1998 


25 


•5967 


45 


•8088 


65 


•9298 


6 


•2288 


26 


•6102 


46 


•8164 


66 


•9340 


7 


2563 


27 


•6237 


47 


•8235 


67 


•9385 


8 


•2821 


28 


•6365 


48 


•8318 


68 


•9427 


9 


•3067 


29 


•6484 


49 


•8396 


69 


•9461 


10 


•3302 


30 


•6612 


50 


•8466 


70 


•9496 


11 


•3527 


31 


•6726 


51 


•8536 


71 


•9531 


12 


•3743 


32 


•6842 


52 


•8592 


72 


•9588 


13 


•3952 


33 


•6958 


53 


■8660 


73 


•9595 


14 


•4152 


34 


•7066 


54 


•8722 


74 


•9620 


15 


•4345 


35 


•7172 


55 


•8779 


75 


•9638 


16 


•4532 


36 


•7276 


56 


•8846 


80 


•9784 


17 


•4712 


37 


•7378 


57 


•8904 


85 


•9878 


18 


•4885 


38 


•7477 


58 


-8962 


90 


•9945 


19 


•5055 


39 


•7567 


59 


•9002 


95 


•9960 


20 


•5219 


40 


•7665 


60 


•9062 


100 


1-0000 



Table No. 3. 

In condensing engines a deduction must be made for im- 
perfect vacuum ; usually amounting to, from 2}4 to 3 pounds 
per square inch. 

The Table No. 3 contains constants for finding the average 
pressure in the cylinder, for any percentage of the stroke (from 



And Its Appliances. 



135 



1 to 100) at which the steam is cut-off, and on account of its 
simplicity, will be found in many cases more convenient in 
finding the average pressure on the piston throughout the 
stroke (from a given initial), than by the ordinary method of 
using hyperbolic logarithm. 

The rule by which to use the constants is as follows : 
Multiply the constant opposite the known per cent of cut-off, 
by the total pressure of the steam entering the cylinder; the 
product will be the total average pressure on the piston. 

AVERAGE PRESSURE OF STEAM IN THE CYLINDER WITH VAR- 
IOUS INITIAL PRESSURES AND DIFFERENT RATES 
OF EXPANSION. 



Initial 
pressure 


Percentage of the stroke at which steam is cut off. 


above 








1 












atmos- 


10 


15 


20 


25 30 


35 • 


40 


45 


50 


60 


phere in 
lbs. per 
sq. inch. 








1 














Average pressu 


re >n lbs. per square inch during th 


e whole stroke. 




40 


18-1 


238 


28-6 


32-8 


366 


39 3 


421 


444 


465 


499 


45 


. 198 


262 


310 


35-8 


392 


43 


460 


48-6 


507 


54 4 


50 


215 


283 


33 8 


38-7 


430 


465 


49 9 


526 


550 


590 


55 


232 


305 


364 


41-7 


462 


502 


535 


567 


591 


633 


60 


247 


32-6 


39 


448 


495 


537 


574 


60-8 


634 


68-0 


65 


264 


348 


417 


47-7 


529 


57 3 


611 


648 


675 


725 


70 


28-0 


370 


441 


506 


561 


609 


650 


688 


71-8 


77-0 


75 


297 


392 


46-9 


537 


594 


643 


68-8 


729 


760 


81-5 


80 


313 


41-4 


494 


56-6 


628 


680 


72-7 


769 


80-2 


86-0 


85 


330 


435 


52-0 


596 


660 


715 


765 


80-9 


844 


906 


90 


347 


457 


547 


627 


695 


75-0 


803 


849 


88-7 


953 


95 


363 


47-9 


575 


65-9 


730 


78-6 


84 1 


89 


93 


1000 


100 


380 


500 


599 


687 


760 


82-2 


S8-0 


93 


973 


104-5 


110 


413 


545 


650 


746 


826 


893 


957 


1010 


105-6 


1130 


120 


447 


58-8 


701 


80-5 


89-3 


965 


1033 


1091 


1140 


1221 


130 


480 


631 


753 


86-5 


960 


1038 


1110 


1172 


1225 


1313 


140 


512 


67'5 


80-7 


92-5 


1026 


1110 


1186 


125:3 


1310 


1404 


150 


546 


719 


859 


98-5- 


T09-3 


1180 


1263 


1334 


1395 


149 5 


160- 


57 9 


762 


911 


104-5 


116-0 


125-2 


1340 


1415 


148 


15S5 


170 


612 


806 


963 


1105 


122-6 


132 4 


141-8 


1497 


1565 


1675 


180 


645 


85 


1015 


1165 


1293 


1397 


1495 


157-9 


1650 


176T. 


190 


679 


893 


1067 


1225 


1360 


146-5 


157'3 


166 


1735 


1857 


200 


711 


937 


1120 


128-5 


1426 


154 


1650 


1740 


1820 


194-8 



Table No. 4. 
From this total, subtract the average back pressure, 
(which will be about Jive pounds in condensing engines, and in 



136 Steam Engine Indicator 

non-condensing engines it will be from one to two above the 
atmosphere, or about sixteen pounds total), the remainder 
will in either case be the average, or mean effective pressure. 

Table No. 4 gives the average pressure of steam in the 
cylinder of an engine for the various initial pressures, above 
the atmosphere in pounds per square inch, and at different 
rates of expansion. 

In the above table, no allowance is made for back pres- 
sure and compression, therefore their effect must be subtracted 
from the above average pressures in order to ascertain the 
mean effective pressure on the piston. 

In non-condensing engines, working under favorable con- 
ditions, the average back pressure will be from 1. to 2. pounds 
above the atmosphere or ordinarily a total of about 16 pounds 
per square inch ; this amount varies according to location, or 
elevation above the sea level. 

In condensing engines the back pressure will average 
about 5 pounds, irrespective of atmospheric pressure. 









And Its Appliances. 137 



CHAPTER XIX. 



THEORY OF ACTION OF STEAM EXPANSION IN CYLINDERS. 



There are three conditions of the steam cylinder, within 
which the action of the steam is differently influenced, as follows : 

1 st. The outer surface may be bare or unprotected by 
any covering whatever and wholly exposed to the surrounding- 
medium. 

2d. It may be covered by some non-conducting material, 
such as felt or asbestos, and this in turn protected by a cover- 
ing of wood or iron on the outside. 

3d. It may be so constructed than an annular chamber 
may be formed on the outside, to be filled with steam from the 
steam chest, steam pipe, or from any convenient place where 
the steam is, of at least, the same temperature as the entering 
steam driving the piston. 

In some cases the cylinder heads are also cast with a 
chamber for containing steam ; this is called steam jacketing, 
and the jacket itself is also covered with a non-conducting 
material. 

Therefore an explanation of the generally accepted theory 
of cylinder condensation may be of assistance to many, and lead 
to a better understanding of the action of steam within the 
cylinder of an engine while in operation, and also explain the 
cause of such condensation ; which invariably occurs, more or 
less, in all steam engine cylinders, 



138 Steam Engine Indicator 

The action of steam in an tmjacketed or exposed non-con- 
densing engine cylinder is about as follows : As the entering 
steam at the commencement of the stroke, is of a much higher 
temperature than the metal parts, with which it comes in con- 
tact; (that is, the interior surface of the cylinder, piston, and 
cylinder head;) consequently a portion of this steam is con- 
densed in heating up these parts, to the temperature of the 
entering steam. 

As the piston moves forward uncovering fresh surfaces of 
the cylinder, the condensation continues until after the admis- 
sion valve closes, or until cut-off takes place. 

This condensation is deposited in form of moisture upon 
the interior walls of the cylinder, also the piston and cylinder 
head ; but does not become apparent on the steam line of the 
diagram, because the place of that condensed, is supplied from 
the steam chest, during the admission of steam. 

After cut-off the steam then commences to expand, and 
both pressure and temperature begin to diminish in a corres- 
pondingly degree ; and unless the steam is cut-off. very early in 
the stroke but little further condensation takes place ; (although 
fresh surfaces of the cylinder that are cooler than the steam, 
continued to be uncovered as the piston advances) for the 
reason that as soon as the temperature of the steam commences 
to fall, through expansion, the head, piston, and walls of the 
cylinder, (already heated to the temperature of the initial 
steam,) begins to impart a portion of their heat to the expand- 
ing steam, and thus prevent further condensation (to any great 
extent) taking place. As represented at A in diagram Fig. 66. 
As the piston continues to advance, the expansion is carried 
still further and in consequence, the temperature, as well as 
pressure, is correspondingly lowered. 

During this time the higher temperature existing in the 
cylinder walls, piston and head, has been gradually imparted 
to the steam condensed in the early part of the stroke, causing 



And Its Appliances. 



!39 



a re-evappration of this moisture and thereby raising the ter- 
minal pressure in the cylinder. Also shown in Diagram 66 
at B. 

When the piston arrives at or near the end of the stroke, 
the exhaust valve opens, and both pressure and temperature of 
the steam immediately falls to an extent corresponding to the 
pressure and temperature of steam at atmospheric or back 
pressure. 

As the metal has still a higher temperature than the ex- 
haust, any remaining water is therefore re-evaporated during 
32 




Fig. 66. 

the return stroke, by absorbing heat from the cylinder walls, 
piston, and head, thereby still further reducing their tem- 
perature ; and this extraction of heat has to be restored to 
these parts again at the expense of the entering steam for the 
next forward stroke of the engine. 

In a very early cut-off in un jacketed cylinders the steam 
suffers further condensation for some distance after the admis- 
sion valve closes, owing to the cooler portions of the cylinder 
surface which are being exposed (by the advance of the piston,) 
having to be heated by the comparatively small volume of steam 
confined within the cylinder after cut-off, and the consequence 



140 



Steam Engine Indicator 



is that the pressure falls for some distance in a much greater 
ratio, than that due to expansion alone. As the piston ad- 
vances however, and the expansion continues, the pressure 
falls, and consequently the temperature of the steam becomes less 
than that of the interior surface of the cylinder, and other 
parts ; thereby causing a re-evaporation of the moisture which 
has been deposited upon their surface during- the earlier part 
of the stroke. The volume of steam present, being thus in- 




Fig 67. 
creased by this re-evaporation, the pressure also becomes 
higher, resulting in a rise of the expansion line during the 
latter part of the stroke. 

Therefore the effect of this action on the expansion curve 
of an actual diagram, with an early cut-off, is to cause it at first 
to fall considerably below, (just after cut-off) and subsequently to 
rise above the true theoretical curve toward the end of the stroke. 

The expansion line of Fig. 67, represents the partial in- 
creased effects of cylinder condensation, that is due to an early 
cut-off, showing the falling below at a point A, and rise above 
at B, of the actual from the theoretical curve drawn in dotted 
line from the point of cut-off C. 



And Its Appliances. 141 

The theoretical curve D, B, is drawn in dotted line from 
the point B, at which the exhaust valve opens, and represents 
the additional work that might be done by steam of a terminal 
pressure T, provided condensation were prevented. 

This deviation from the true curve is greatly increased by 
water held in suspension or entrained in the steam. 

It is therefore important that the initial steam be prac- 
tically free from moisture. 

The mutation of heat back and forth, (which occurs at 
every stroke) between the steam, and the interior surface of 
the cylinder as well as the cylinder head and piston, take place 
very quickly, and effects the metal of these parts to a slight 
depth only ; as there is not sufficient time for it to penetrate 
very deeply, especially in high speed engines. 

Steam Jacketed Cylinders. The action which takes place 
in a steam jacketed cylinder of a condensing engine is some 
what different ; as the following description will indicate : 

In such cases the jacket is arranged to be supplied con- 
stantly with direct steam (either through the steam chest, or 
steam pipe) of the same temperature and pressure as the initial 
steam entering the cylinder ; consequently the alternate heat- 
ing, and cooling of the metal that occurs in an unjacketed cyl- 
inder, will in a great measure in this case be prevented; 
hence, comparatively no initial condensation takes place, and 
the steam will enter the cylinder without apparent loss. 

The piston itself being partially under the same conditions 
as before, will tend continuously to condense a very small por- 
tion of the steam; but this condensation, (in the act of form- 
ing) will at once be re-evaporated ; therefore no actual conden- 
sation takes place during expansion, as the quantity of heat 
that disappears in doing work is steadily supplied by the 
cylinder walls. 



142 Steam Engine Indicator 

The walls in turn absorb heat from the steam in the jacket, 
thereby condensing a portion of the steam, but the jacket 
being constantly supplied with direct steam, maintains the 
cylinder at nearly a uniform temperature. 

When the exhaust valve opens, and communication is 
made with the condenser, (there being no water or moisture to 
re-evaporate,) a further expansion of the steam occurs ; there- 
by lowering both pressure and temperature. 

This exhaust steam being comparatively dry, receives and 
parts with heat slowly, and therefore does not absorb as much 
heat from the cylinder walls when expanding into the con- 
denser, as the wet steam from an unjacketed non-condensing 
cylinder; as in the former case. 

Although the steam jacket supplies the heat necessary to 
prevent condensation, and also to heat up the cylinder, from a 
temperature corresponding to the exhaust, to that of the initial 
or entering steam ; yet this quantity of heat is much less than 
that which is extracted by wet steam from the walls of 
cylinders that are unjacketed, consequently the actual gain 
effected by the use of a steam jacket on a cylinder, is, the 
difference of saving, between the prevention of condensation 
in the cylinder during the first part of the stroke, and the loss- 
that occurs in heating the exhaust steam during the return 
stroke ; and this gain may in many cases be very slight, as the 
saving depends principally upon the fact that steam absorbs 
heat much slower than water. 

In preventing this condensation in the cylinder, the heat 
abstracted from the steam jacket, transfers all liquefaction or 
condensation of the steam to the jacket ; and on this account, 
some engineers at the present time, questions its utility in the 
matter of economy, (also considering first-cost) and claim that 
the condensation, and waste of steam in the jacket, is more 
than that lost or wasted in unjacketed cylinders ; the excess 



And Its Appliances. 



I4J 



being due to increased condensing, and radiating surface of 
the jacket, above that of the steam cylinder. 

The diagram represented in Fig. 68 is from a steam jack- 
eted cylinder and it will be seen that the actual curve agrees 
very closely to the Isothermal. 

In reference to the efficiency of the jacket however, all re- 
sults depend in a great measure upon its proper construction, 
and appliances ; and also in providing means for the removal 
of all air and water arising from condensation ; and utilizing 
-33 




Fig. 68. 
such water, as fast as formed by returning it to the boiler ; 
thereby preventing the accumulation of either in the jacket. 

In addition to this and to insure the best efficiency it is 
absolutely essential that the jacket be constantly supplied with 
dry steam of a temperature fully as high, in all cases, as that 
of the initial steam entering the steam cylinder ; and more es- 
pecially in engines with early cut-off, and consequently high 
expansion. 

Where the details referred to, are strictly observed and 
carried out, the result must evidently tend more or less to 



144 Steam Engine Indicator 

better economy and efficiency in engines, by the use of the 
steam jacket. 

On the contrary, if wet steam, or steam containing a large 
proportion of moisture be introduced into a steam jacketed en- 
gine cylinder in the beginning of the stroke, a result will fol- 
low, which will be the opposite of economy, and end in con- 
siderable loss, this loss arising from the large quantity of heat 
abstracted from the jacket during the stroke, for the evapora- 
tion of this water or moisture that has entered the cylinder. 

Therefore to insure that the economy and efficiency which 
is expected from the use of the steam jacket be realized, it is 
very essential that all the requirements before mentioned for 
its proper performance, should be assured, otherwise the jacket 
may be quite ineffectual ; its theoretical efficiency wholly 
destroyed, and its utility consequently questioned. 

In a great majority of cases at the present time, cylinder 
jacketing is accomplished in accordance with the second con- 
dition mentioned ; viz, that of thoroughly covering the whole 
of the exterior surface of the cylinder, and steam chest, with 
some non-conducting material as felt, wool, or asbestos, and 
secured thereto by an extra covering of wood or iron ; com- 
pletely enveloping the whole. 

This combination of covering where suitably applied, ap- 
pears to give general satisfaction, as many builders of our 
best modern engines testify ; by the almost exclusive use of 
some suitable material for cylinder jacketing, on this prin- 
ciple. 

Also in many cases where engine cylinders are covered 
and protected in the manner just described, and having steam 
tight valves, and piston, it is frequently found that the expan- 
sion line of the diagrams therefrom, agree very nearly with 
the isothermal or true theoretical curve as represented in 
Fig. 69. 



And Its Appliances. 145 

Therefore it is readily seen from the diagrams Fig. 68 and 
Fig. 69 the advantages to be derived by either of the latter 
conditions or methods of cylinder jacketing, to secure the 
greater economy, and efficiency in the engine ; above that of 
one from an exposed or unprotected steam cylinder with an 




Fig. 69. 
early cut-off as represented in the diagram Fig. 6y. In order to 
obtain Indicator diagrams that shall be accurate exponents, 
and represent the true action of steam expansion within the 
cylinder, it is absolutely essential that the valves, and piston 
of the engine be practically steam tight ; and also that the In- 
dicator itself have perfect and unimpeded freedom of move- 
ment in all its parts, when under pressure and temperature of 
the steam present. The exact measure of the tension, or in 
other words, the strength of the spring used, is also of great 
importance ; as the accuracy of all computations based upon 
the form of the diagram, for obtaining the Mean Effective 
Pressure, acting against the piston depends upon the correct- 
ness of the spring; therefore its accuracy should be determined 
and established, (by comparison with a correct steam guage), 
before any elaborate tests are anticipated. This may be ac- 
complished in a satisfactory manner by means of the simple 
Indicator spring testing device represented and described in Fig. 
84, Chapter XXII. 



146 Steam Engine Indicator 



CHAPTER XX. 



READING THE DIAGRAM. 



The principal and most positive information to be derived 
from trie reading of an actual indicator diagram, is, the meas- 
ure of the force or pressure in the cylinder, acting upon the 
opposite sides of the piston, at any and all points, during 
one complete revolution of the engine ; hence the actual card, 
as compared with the theoretical diagram, (under similar con- 
ditions) indicates the efficiency and economy of the engine ; 
and all other information must also be acquired through ex- 
ceedingly careful consideration, and reasoning in the study of 
the diagrams ; and conclusions arrived at, therefrom in accord- 
ance with an exercise of the best judgment of the engineer. 

The figures traced by the pencil will vary in outline in 
different engines, and also from the same engine under vary- 
ing conditions, due to a number of causes ; as leakage of valves, 
condensation and re-evaporation of the condensed steam in 
the cylinder, construction and the adjustment of valves, condi- 
tion of the steam, etc. 

These effects will be more apparent along the expansion 
curve especially ; and as a consequence the actual curve will 
very rarely coincide exactly with the true theoretical curve. 

Therefore it is very essential that all cards traced by the 
indicator should accurately represent the duty performed by 
the engine ; as the accuracy of all such investigations depends 
entirely upon the correctness of the diagrams. 



And Its Appliances. 



147 



Upon an examination of the steam expansion curve of in- 
dicator diagrams it will be found (almost invariably), that the 
Terminal pressure is relatively too high (from a given cut-off), 
as compared with the true theoretical curve ; the amount in- 
creasing as the ratio of expansion increases: as shown in 
Fig. 66 




Fig. 70. 

This result may be due to either of two causes, or to both 
combined. 

1st. To leaky steam or admission valves, through which 
the steam is enabled to pass into the cylinder, after the closure 
of such valve ; or in other words, after the point at which cut- 
off is supposed to have taken place ; and thereby producing a 
higher terminal, than would otherwise appear with steam tight 
valves. 

2nd. To a re-evaporation of the entering steam that is 
condensed in the earlier part of the stroke, through coming in 
contact with the interior walls of the cylinder, which have been 
cooled to a temperature corresponding to the lower pressure of 
the escaping steam, during its exhaust. 



148 Steam E?igine Indicator 

In some cases however the expansion curve of the actual 
diagram will be found falling below the true or theoretical 
curve throughout its entire length ; as shown in Fig. 70, evi- 
dently due, to leaky piston, and exhaust valves; this, also in 
connection with exposed or unjacketed steam cylinders. 

But it frequently happens that cards are found wherein 
the expansion curve coincides very nearly with the isothermal 
or theoretical, although they have been taken from engines in 
which both valves and piston are known to leak badly. 

In such cases the leakage through the admission valve 
after closing is just sufficient to restore the steam lost through 
a leaky piston, and the result under such circumstances, are 
that the two curves will be a very near approach to each other. 

Such cards from observation alone have the appearance of 
good efficiency and economy in the engine ; when in fact the 
opposite of this prevails, and an extravagant loss and waste of 
steam is the consequence ; all arising from a leaky condition of 
these parts. 

The loss of steam from this cause, and also from cylinder 
condensation is not accounted for by the indicator, hence does 
not appear in the diagrams, and is only made apparent by a 
comparison of the water consumption per horse power (as com- 
puted from the diagram), with the actual amount of water that 
has been supplied to the boiler. . 

An important matter to be ascertained in reference to all 
indicators ; is, whether the vertical or admission line on the 
diagram, made by the pencil (when in contact with the paper 
on the drum) is exactly perpendicular to the atmospheric, ot 
horizontal line, that is made by the pencil, when in contact 
with the drum while rotating. 

A leaning of the admission line either forward or back, 
thereby causing it to be out of square with horizontal line, 
tends to be misleading in reference to the proper adjustment 
of the valves, especially if a fault of this kind exists in the 



And Its Appliances. 



149 



instrument, and not previously known. This fact may easily be 
determined at any time before placing the spring in the instru- 
ment, by simply placing the paper upon the drum the same as 




Fig. 71. 

for taking diagrams, and bring the pencil in contact with it ; 

then cause the drum to rotate once back and forth by means 

of the cord attached to the indicator, thereby making a hori- 

A 




Fig. 72. 
zontal line on the paper ; then mark a perpendicular to this by 
raising the pencil by hand to its extreme height, Remove the 



150 



Steam Engine Indicator 



paper from the drum, and compare its correctness with any- 
ordinary square or right angle triangle at hand, as shown in 
Fig. 7 1 . Any inclination or leaning of the admission line in 
indicator diagrams, either forward or back, as in Fig. 72 and 
Fig. 73, is usually construed and considered to be an im- 
proper adjustment of the valves. 

For example. In reviewing the diagram represented in 
Fig. 72 ; from the fact of a leaning forward of the admission 
line, the time of opening of the valve for steam admission, 
would ordinarily be assumed to be too late, or indicating in- 
sufficient lead ; and in consequence the piston has advanced a 
portion of the stroke, (as shown at A), before the initial pres- 
sure has reached its highest point ; resulting to a certain de- 
gree, in a loss of power, and efficiency in the engine. 

Again suppose in a diagram the results are as represented 
in Fig. 73, where the admission line inclines outward; this 




Fig. 73. 

might indicate either a too early opening of the steam valve, 
thereby admitting steam in the cylinder before the piston had 
completed the stroke ; or a too early closing of the exhaust at 
that end of the cylinder, thus causing excessive compression ; 
either of which would also cause a loss of efficiency and power. 



A nd Its Appliances. 151 

Most types of indicators after their being in use for a 
length of time, are liable to certain defects, or disarrangement 
more or less in their pencil movement ; (and these defects some- 
times appears in new instruments) and which prevents the ini- 
tial pressure or vertical line as traced upon the paper, from be- 
ing at a right angle or perpendicular to the atmospheric line ; 
and in such case the instrument is usually designated as out of 
square. 

As a consequence, the admission line at either end of the 
diagram, will be inclined to the perpendicular, as appears by 




Fig. 74. 
the dotted lines A, A, in the diagrams Fig. 74, and which may 
be wholly due to such incorrectness in the indicator as stated ; 
notwithstanding the valve adjustment of the engine may be 
practically all that can be desired. 

This discrepancy very often arises from careless handling, 
and from culpable neglect, and abuse of the instrument in var- 
ious ways. Where a defect of this description exists in the in- 
strument, it is generally advisable to send it at once to the 
maker, to insure that the necessary correction be properly and 
satisfactorily accomplished. 



152 Steam Engine Indicator 



CHAPTER XXI. 



DIFFERENT METHODS OF COMPUTING THE AMOUNT OF STEAM 
ACCOUNTED FOR BY THE INDICATOR. 



If the number of cubic feet occupied by the steam in an 
engine cylinder, and the pressure it exerts against the piston 
at any point of the stroke be known, the number of pounds 
which the steam weighs may be computed. 

The weight of the steam at any point, less the weight re- 
maining in the cylinder at compression, is the weight account- 
ed for by the indicator. 

The weight accounted for on one stroke, multiplied by 
the number of strokes per hour, and divided by the indicated 
horse power, is the amount of steam accounted for, per indi- 
cated horse power per hour. 

This computation requires a knowledge of the volume of 
the clearance space in the cylinder; that is, the cylindrical 
space between the cylinder head and the piston, when the pis- 
ton is at the end of its stroke, and also includes the volume of 
the steam ports and passages which conducts the steam from 
the admission valve to the cylinder, and also from the cylinder 
to the exhaust valve. 

The water consumption of an engine (as stated in another 
chapter) is the measure of its economy, but the exact amount 
is not determinable from the diagram, because that gives the 
pressure of stea?n only. 



And Its Appliances. 



153 



Of the water that has been carried over with the steam, or 
of the steam that has been condensed by coming in contact 
with the comparatively cold surfaces of the cylinder, the dia- 
gram gives no record. 

We know however, that at least, the amount of steam ac- 
counted for by the indicator has passed through the cylinder ; 
and in fact, we know that sometimes a much larger amount 
has been used. 

One method of ascertaining the amount accounted for by 
an indicator is to calculate the piston displacement, plus the 
clearance space for a given time, in cubic feet, up to a certain 
point in the stroke before the exhaust opens, and multiply this 
volume by the weight of a cubic foot of steam of the absolute 
pressure at this point. 




1r V- 

Fig. 75. 

This method is described in the diagram Fig. 75 and is as 
follows: Draw the vacuum line V. V., and the clearance line 
D. and select some point on the expansion curve, as at C- 
where it is known that both the steam and exhaust valve are 
closed and wherever it is possible, have this point C. at a 



154 Steam Engine Indicator 

distance from the end of the diagram equal to the clearance dis- 
tance D. 

Where this can be done, then the volume to point C, in- 
cluding clearance, will just equal the piston displacement 
which is the area of the piston multiplied by the length of 
stroke. 

Where this cannot be done, then find volume to point C, 
including clearance, which if multiplied by the weight of a 
cubic foot of steam of the absolute pressure at the point se- 
lected will give the weight of the steam contained in the cylin- 
der at such point. 

The volume at point C may be found as follows : 

Assume the cylinder of an engine to be 12 inches in diam- 
eter, (113.09 square inches in area) with a stroke of piston of 
30 inches running 90 revolutions per minute ; the area of pis- 
ton rod being 6.18 inches; the clearance being five per cent, 
and the scale of the spring 40. 

From the area of the cylinder, deduct one-half the area of 
the piston rod (6. 18-1-2 = 3.09 inches) hence; 1 13.09—3.09= 1 10 
square inches as the mean area of the piston. 

The total piston displacement per stroke therefore will be, 
the mean area of piston in inches multiplied by length of 
stroke, also in inches, 110x30=3300 cubic inches per single 
stroke of the engine. 

The displacement to the selected point C, may then be 

ascertained, by multiplying the total displacement, (3300 cubic 

inches) by the distance that point C, is from the initial end of 

the diagram, or from line E, and dividing this product by the 

total length of the diagram, or line A, B, for example: The 

length of the line C, E, is 3.56 inches, and the length of A, B, 

3 "2 00 X 3 ^6 
is 3.75 inches, therefore — ^- = 3132.8, cubic inches. 

To this must be added five per cent, for clearance, or 
3300X .05= 165. then 3132.8+165 = 3297.8 cubic inches occupied 



A nd Its Appliances. 155 

t>y steam at point C. The engine running 90 revolutions 
per minute consequently makes 90x2x60 = 10800 single 
strokes per hour ; therefore the displacement per hour is 

±_zLl =20611 cubic feet. 

1728 

Now with the scale of the spring, (40) with which the dia- 
gram was taken, measure the absolute pressure from the va^ 
cuum line to point C, and opposite this pressure in the Table 
No. 8 of properties of saturated steam will be found the weight 
of a cubic foot of steam at that pressure. . 

The absolute pressure at point C, is 26 pounds and the 
-weight of a cubic foot of steam at this pressure is .065, hence 
the weight of steam at this point per hour is 2061 1 X .065 = - 
1339.71 pounds. 

From this amount however the steam saved by compression 
caused by the closing of the exhaust valve before the end of 
the stroke, must be deducted; the remainder being the actual 
consumption of steam as accounted for by the indicator* 

The process by which to ascertain the amount of this de- 
duction is as follows : 

From the selected point C, draw a line parallel with the 
vacuum line to E, intersecting the compression curve at point 
F. ; multiply the accounted consumption by the distance from 
C to F, and divide this by the distance from C. to E. 

The length of the line from C. to F. is 3.32 inches, and 
that of the line from C. to E. is 3.56 inches, hence 

I^^Q 71X3 ^2 

^ — — 1249,39 pounds of steam exhausted per hour, 

corrected for both clearance and compression. The Mean 
Effective Pressure of the above diagram (measured by Plani- 
meter) being 37.5 pounds per square inch, the Horse Power is 

^— 1 — j^_ — 56.25, hence the steam accounted for per 

33000 I2 4 Q ^Q 

horse power per hour will be — ^^ — 22.21 pounds. 



i S 6 



Steam Engine Indicator 



A somewhat simpler method of determining the same re- 
sult, is to continue the expansion curve of the diagram in its 
gradual descent, to the end of the stroke, and by that means 
locate the terminal pressure as at T, Fig. 76. 




^.--^T 



Fig. 76. 

This point may be found according to the method des- 
cribed for constructing the theoretical curve as explained in 
Fig, 56 Chapter XIV, or may be traced by hand from the point 
of exhaust opening on the expansion curve, to the completion 
of the stroke ; and which will be sufficiently near in cases 
where no great accuracy is desired. 

The process by calculation is to find the total mean dis- 
placement of the piston for the whole stroke, plus the clearance 
in cubic feet per hour. 

Multiply this by the weight of a cubic foot of steam at the 
terminal pressure T, and divide this product by the Indicated 
Horse Power. 

The quotient is the number of pounds of steam entering 
the cylinder per horse power per hour. For example : Assum- 
ing the engine data to be the same as in the preceeding 



A nd Its Appliances. I 5 7 

example ; therefore the mean piston displacement per single 
stroke in this case will be 3465 cubic inches; which if multi- 
plied by 10800 the number of single strokes per hour, and di- 
vide by (1728) the number of cubic inches in a cubic foot, the 
quotient will be the total piston displacement in cubic feet per 

1 .1 . ■ 3465 X 10800 ■ , 

hour, that is, ^ D = 21656. 

1728 D 

The absolute terminal pressure being 25 pounds per square 
inch, the weight of a cubic foot of steam at that pressure, ac- 
cording to the table is .063 pound; therefore 2i656x.o63 = 
1364.32 pounds, which divided by the indicated horsepower 
of the diagram (56.25) is equal 1353.50-^-56.25 = 24.25 the num- 
ber of pounds of steam entering the cylinder per horse power 
per hour. 

And this would also be the actual amount of steam ex- 
hausted, were it not for the fact that it is exhausted above va- 
cuum from which the pressure is calculated ; also a portion of 
it is saved in the clearance space upon the return of the piston, 
and this saving is still further increased by the closure of the 
exhaust valve before the end of the stroke ; therefore the actual 
indicated consumption will be minus this amount. 

This correction may be made as follows : 

From the terminal pressure T, draw a line T 2, parallel 
with the vacuum line, thereby intersecting the compression 
curve at 1, at which point the quantity of steam exhausted 
from the clearance has been restored, and the consumption will 
be as much less than the rule shows, as the line T. 1. is shorter 
than the line T. 2. or the length of the diagram. 

Consequently to find the corrected rate, multiply the result 
as found by the rule (24.25) by the length of the T. 1 . = 3.47 
inches, and divide by the length of the line T. 2=3.75 inches, 

hence — ^—==22.43 pounds per Indicated Horse Power 

3-75 
per hour ; the corrected rate for both clearance and compression. 



158 Steam Engine Indicator 

The volume of the cylinder, and the number of strokes 
being factors in the computation of the amount of steam ac- 
counted for in any given time, and the same also being factors 
in the calculation of power developed, consequently for this 
reason it is not necessary to take these quantities into consid- 
eration, when only the amount accounted for per horse power 
per hour is desired. 

The above fact provides another, and much more simple 
method of computing the rate of water consumption ; in which 
the piston displacement is not required, and which is indepen- 
dent of any knowledge of the size or speed of the engine ; the 
diagram alone being sufficient ; but it is necessary however to 
know the mean effective pressure. 

This rate may be found by the following rule : Divide 
the constant number 859375 by the volume of steam at the ter- 
minal pressure, and by the mean effective pressure. 

The quotient will be the water consumption per horse 
power per hour uncorrected for compression and clearance. 

This correction is made in the same manner as that given 
in the previous method. 

This constant 859375 is the number of pounds of water 
that would be used in one hour by an engine developing one 
horse power, if run by water, (instead of steam) at one pound- 
pressure per square inch. 

The process is based on the following considerations : A 
standard horse power is 33000 pounds raised one foot per min- 
ute, or 33000 foot pounds, which is 33000x60=1,980,000 foot 
pounds per hour, or 1,980,000X12 = 23,760,000 inch pounds 
per hour. The latter number of pounds on being raised one 
inch per hour, requires the same expenditure of energy, as to 
lift 33000 pounds one foot per minute ; each being the equiva- 
lent of the other. 

Now suppose the engine to be run by water, (instead of 
steam) at one pound pressure per square inch, and the number 



A nd Its Appliances. 



59 



of cubic inches in a pound of distilled water being 27.648 then 
23,760,000-1-27,648=859375 which is the desired constant, 
and which is the number of pounds of water per indicated 
horse power per hour that would be consumed by an engine 
driven by water, (instead of steam) at one pound mean effect- 
ive pressure. 

Example : Assume the diagram shown in Fig. y/, to be 
one from an engine of 12 inches, diameter of cylinder, and 24 




Fig. 77. 

inches stroke running 100 revolutions per minute, the scale of 
the spring 40. 

The mean effective pressure of the diagram is found to be 
42 pounds per square inch, when measured either by ordinates 
or by planimeter. 

The absolute terminal pressure T. V, is 28 pounds, and 
the volume at that pressure (as given in table No. 8) is 
883, that is one cubic inch of water at a temperature of 60 de- 
grees, makes 883 cubic feet of steam at 28 pounds pressure per 
square inch. 



160 Steam Engine Indicator 

nee by the rule the rate of water c 

= 23.17 of water per indicated horse power per hour. 



Hence by the rule the rate of water consumption will be 
859375 



883X42 

But in this case some steam is saved by the- closure of the 
exhaust valve before the end of the stroke, while some is 
wasted by exhausting from the clearance at a pressure greater 
than the back pressure, and the above calculation so far makes 
no allowance for either. 

This allowance for compression and clearance may be cal- 
culated by the following method : 

Locate the point T on the diagram where the expansion 
line would have terminated, provided the steam had not been 
released until the end of the stroke. 

Draw the line T. 2, parallel with the atmospheric line A. 
A, which will intersect the compression curve at 1, at which 
point the quantity of steam exhausted from the clearance has 
been restored ; therefore the consumption will be as much less 
than the rule shows, as the line T. 1. is shorter than the line 
T. 2, or the length of the diagram. 

Multiply the result obtained by the rule, by the length of the 
line T. 1, and divide the product by the length of the line T. 2 ; 
the result will be the rate of consumption corrected for both 
clearance and compression. 

Example: The length of line T. 1, is 3.47 inches, and 
the length of line T. 2, is 3.75 inches. The rate of consump- 
tion obtained by the rule is 23. 17, hence 2317x3.47^3.75 = - 
21.43 pounds; the corrected rate per indicated horse power per 
hour. 

This latter method is most generally employed by engin- 
eers in charge of plants, as it gives a very close approximation, 
and is very much more convenient than computations made 
from the steam displacement of the cylinder. 

Where diagrams are taken that have only a small amount 
of compression, the line T. 1, will not intersect the compression 



And Its Appliances. 



161 



curve; as in Fig-. 78. In such cases it is necessary in order to 
find the length of the line T. 1, to continue the curve from the 




Fig. 7 



end of the diagram, (being guided by the eye) upward in about 
its natural direction, and far enough beyond the end of the 
diagram, as to be intersected by the line T. 1, which is always 
drawn parallel with the atmospheric line, as shown by the 
dotted lines in Fig. 78. 

The line T. 1, will therefore be lengthened, but whatever 
may be its length, it is always the multiplier in making the cor- 
rections, while T. 2, is always the divisor, and represents the 
length of the diagram. 

In this case the result obtained by the rule is increased, 
because the multiplier T. 1, is longer than T. 2. 

In diagrams like Fig. 79 where there is no compression, 
the proper position for point 1 on the terminal pressure line 
may be found as follows : First draw the vacuum line V, and 
locate the clearance line C, in accordance with the best data at 
hand ; then draw the terminal pressure line extending from 



1 62 



Steam Engine Indicator 



T. to C, which will intersect the end of the diagram at point 2, 
and from point 2, draw a diagonal line to the intersection of 
clearance line with the vacuum line ; (see 2 V). 




Fig. 79. 

This diagonal will intersect a continuation of the back 
pressure line at F, directly under the proper place for point 1; 
on the terminal. In this case as in Fig. 78, the result ob- 
tained from the rule will be increased, because the multiplier 
(distance T. 1.) is longer than T. 2 in the correction. 

A knowledge of existing clearance is necessary, as such 
diagrams give no information in regard to it. But the expan- 
sion curve of a cut-off diagram however, does furnish the in- 
formation necessary to arrive at approximately at the volume 
of clearance, unless the curve is very irregular in its forma- 
tion. Diagram Fig. 50 illustrates the method of establishing 
the clearance line by means of the expansion curve. 

The diagram Fig. 80 illustrates one process of locating 
the point 1, (T. 1.) in the terminal line, when this line is be- 
low the atmospheric line, and consequently below any part of 
the compression curve defined on the diagram. 



A nd Its Appliances 



163 



Locate the terminal line by drawing from T, (the terminal 
pressure) a line parallel with the atmospheric line and 
intersecting the end of the diagram at 2. Select any point in 
the compression curve as at D. 




V V 

Fig. 80. 

From that point draw a line perpendicular to the atmos- 
pheric line to terminal line as at F. Then from V where the 
clearance line intersects the vacuum line, draw a diagonal line 
through point F, to point E, (same height as point D.) then a 
line drawn perpendicular to the atmospheric line, from E, will 
intersect the terminal line at the proper place for point 1. 

The process will be recognized the same in principle as 
that used for finding a point in the isothermal expansion 
curve. 

The water consumption computed for diagram Fig. 80 is 
as follows : 

The mean effective pressure as measured by planimeter is 
2}i pounds per square inch, and the terminal pressure is 7 
pounds absolute. 



164 Steam Engine Indicator 

ids as given 

122.5 pounds uncorrected for com- 



The volume for 7 pounds as given in the Table No. 8, 
is 3300, hence 859375 



pression. 3300x2.125 

Line T. 1, is 2.60 inches long, and lineT. 2C(or the whole 
length of diagram) is 3.75 inches, hence 122.5x2.60-^-3.75 = 
84.93 pounds per indicator horse power per hour, the correct 
rate. 

Diagrams similar to Fig. 80 are wasteful of steam, and are 
usually obtained from engines having insufficient load, and a 
comparison of the water consumption, (as computed) with that 
of diagrams taken from moderately loaded engines will at once 
make apparent the economy of the latter, as against the extrav- 
agant waste of the former. 

Probably no other single condition is so detrimental to 
good economy as an engine over large for its work, as a too 
light load necessitates an early cut off; the expansion and con- 
sequent fall of temperature becomes excessive, and hence in- 
ternal condensation appears to the fullest extent. 

In the computation for water consumption of these dia- 
grams it must be understood that the rates as calculated are 
theoretical, and assumes perfect conditions, such as dry steam, 
entire absence of loss from leakage, condensation, etc. 

The diagram shows only the minimum amount of steam 
that has' been consumed by the engine to do a given amount of 
work, and there are many reasons why this consumption of 
water as shown by the indicator should be less than the actual 
amount. 

It is considered that the percentage of loss in a modern 
and properly constructed steam plant is fully twenty per cent. ; 
and taking the engine alone, is at least ten per cent, and this 
may be still further increased by condensation, and also where 
considerable leakage occurs, etc., so that it is safe to add at 
least 10 per cent, to the indicated consumption to closely ap- 
proximate the actual consumption. 



A nd Its Appliances . 165 

The loss from water that is carried over with the steam is 
chargeable to the boiler, and not to the engine. 

The unindicated loss will also be greatest at light loads. 
With steam at 80 pounds pressure, and a mean effective pres- 
sure of from about 40 to 45 pounds, (corresponding to about 
one-fourth cut-off), will give the least loss. 

Very short cut-off gives an increased loss. 

The steam used in the low pressure cylinders of compound 
engines, first passes through the high pressure cylinder ; hence 
the water consumption as computed for the high pressure 
cylinder, (corrected for compression^ will be the measure of 
consumption for the whole engine. 

This amount is to be divided by the horse power of the 
whole engine for the consumption per indicated horse power 
per hour. 

The consumption may also be computed from the low 
pressure cylinders in the same manner as for the high pres- 
sure cylinder ; but which will be found to disagree with the 
former owing 1 to some loss between the cylinders. 

It will also be found that if no other steam is admitted to 
the low pressure cylinders, except what has already passed 
through the high pressure cylinder, that the water consump- 
tion will appear greatest when calculated from the high pres- 
sure, and will gradually become less from each successive 
cylinder: therefore it is a good plan, and of interest to meas- 
ure the consumption from each and all of the cylinders, and 
compare the results. 

The differences may be considered as fair measures of the 
loss in transmission between the cylinders. 

Another method is here given for calculating the water 
consumption by constant, and which is also independent of any 
knowledge, (except the mean effective pressure) of the size or 
speed of the engine ; and which may be easily and accurately 
determined from the diagram, for both cut-off, and release by 



1 66 Steam Engine Indicator 

means of, and the use of the formula : J ' J X (proportional 

M. x!/. Jr. 

volume at cut-off X weight of steam) minus, (proportional vol- 
ume at compression X weight of steam)= number of pounds 
of steam accounted for at cut-off, per indicated horse power 
per hour. 

Or, by the formula : , , {? -p X (proportional volume at 

release X by weight of steam) minus, (proportional volume at 
compression X weight of steam)= number of pounds of steam 
accounted for at release per indicated horse power per hour. 

The following is the explanation of the above formula : 

M. E. P. is the mean effective pressure. In compound, 
triple and quadruple expansion engines, this is the sum of two 
or more quantities. 

One is the M. E. P. of the cylinder under consideration, 
as for instance, the high pressure cylinder, and the others are 
the M. E. P. in the other cylinders referred to the high pres- 
sure cylinder. 

The proportional volume at cut-off is the percentage of the 
stroke computed at cut-off, (as at D. Fig. 81) added to the per- 
centage of clearance, and this is to be multiplied by the weight 
of one cubic foot of steam at the cut-off pressure. 

The proportional volume at compression is the percentage of 
the return stroke uncompleted at compression added to the 
percentage of clearance, and this is to be multiplied by the 
weight of one cubic foot of steam at the pressure where com- 
pression begins. 

The proportional volume at release is the percentage of 
the stroke completed at release added to the percentage of 
clearance, and this is to be multiplied by the weight of one 
cubic foot of steam at the pressure where release is taken. 

The constant 13750 is the volume of steam in cubic feet 
per hour required by an engine without clearance to develop 



And Its Appliances. 



167 



one horse power when working - with one pound pressure per 
square inch and without expansion. This quantity will be 
less in proportion to the increase of average pressure ; there- 
fore it is divided by the mean effective pressure (M. E. P.) of 
the diagram. 

The quantity will also be increased in proportion to the 
percentage of clearance, and decreased by the quantity of steam 
saved by compression. 

The points of cut-off, release, and compression referred to 
are shown respectively at D. E. and F. in the diagram Fig. 81. 




Fig. 81. 

The pressures at these points must be the absolute pres- 
sure, taken from zero or a perfect vacuum, which is 14.7 
pounds below the atmosphere when the barometer indicates 
29.92 inches. 

Where great accuracy is desired, the height of the barom- 
eter should be observed, when the diagrams are taken in order 
that the atmospheric pressure which it shows should be used 
in such cases. 



1 68 Steam Engine Indicator 

The pressure of the atmosphere as shown by the barome- 
ter in inches of mercury should be multiplied by 0.491 to re- 
duce it to pounds per square inch. 

The requisite data for computing the amount of steam ac- 
counted for, from the diagram Fig. 81 is as follows : The pro- 
portion of stroke completed at cut-off D, is thirty-hundredths, 
(.30) and the absolute pressure of steam per square inch at that 
point is eighty-three (83) pounds. 

The weight of a cubic foot of such steam is .1967 pounds. 

The proportion of stroke completed at release E, is ninety - 
hundredths (.90) and the absolute pressure thirty (30) pounds. 

The weight of a cubic foot of such steam is .0755 pounds. 

The proportion of the return stroke uncompleted at com- 
pression F. is ten-hundredths (.10) the absolute pressure is 
sixteen (16) pounds, and the weight of a cubic foot of this 
steam is .0413 pounds. 

The clearance of the engine equals .02 per cent. 

The mean effective pressure on the piston is forty (40) 
pounds per square inch. Hence by this method the amount of 

steam accounted for at cut-off will be _AZ_L_ x(.3o-f- .02). 1967 — 

40 

(. 10-f-. 02). 0413 = 343.75 X -0579= 19.90 poundsof steam or water 

per indicated horse power per hour. 

The amount of steam accounted for at release will be : 

-^-5-X (.90+. 02). 0755 - (.IO+. 02). O4I 3= 343. 75 X. 0645 = 22. 17 
40 

pounds of steam per hour. 

Suppose in the engine to which these calculations ap- 
ply, an actual feed water test gave a consumption of thirty 
(30) pounds of water per indicated horse power per hour; 
then the percentage of feed water accounted for at cut-off is 

10.00 sr j / 22.17 

y y =.663 and at release ^—=.739, 

30 30 



And Its Appliances. 



169 



The formula for release may be simplified in cases where 

there is a sufficient amount of compression, by locating the 

compression point at such a height on the compression curve as 

will make that pressure and the release pressure equal, as 

shown in diagram Fig. 82. 

13750 
The formula then becomes (percentage of stroke 

completed at release, minus percentage uncompleted at com 
pression) multiplied by the weight of a cubic foot of steam at 



release pressure, thus, 



13750 



(.90— .10). 0755 = 20. 62 pounds, 



M. E. P. 

the effect of clearance disappearing. The quantity in the 
parenthesis is the proportion which the distance (1) between 
the points in Fig. 82 bears to the whole length of the diagram 




<- - 



L, - 



Fig. 82. 



or to L. That is the proportion 1 



This applies only to the 



release formula. L 

The calculation of the quantity , , ' ^ in these formulas 
• n J M.E. P. 

may be facilitated by reference to following Table No. 5, 



170 



Steam Engine Indicator 



QUANTITY OF STEAM ACCOUNTED FOR BY 
INDICATOR. 



M.E.P. 


13750 


M.E.P. 


13750 


M E.l 


3 13750 


M.E.P. 


13750 


lbs. 


M.E.P. 


lbs. 


M.E.P. 


lb:;. 


M.E.P 


lbs. 


M.E.P. 


10. 


1375,0 


36.5 


376.8 


66. 


208.3 


119. 


"5-5 


IO.5 


1309.6 


37- 


37J 6 


6.7. 


205.2 


I20, 


114. 5 


II. 


I250.O 


37-5 


366.7 


68. 


202 .'2 


121. 


113. 6 


1I.-5 


1V9S.6 


%• 


361.9 


69. 


199-3 


122. 


112.7 


12. 


i 145. 8 


38.5 


357-2 


7o 


I96 4 


t2 3 


in. 7 


12-5 


1100.0 


39 


352.6 


7i 


193-7 


I24. 


no 8 


13- 


1057 7 


39-5 


348 2. 


72 


191. 
188 4 


125. 


no 


13-5 


1008.6 


40. 


343 8 


73 


126. 


^09.1 


14- 


982.1 


40.5 


339-6 


74> 


185.8 


127. 


108 2 


14-5 


948.2 


41. 


335 4 


75 


1833 


128. 


107 4 


»5- 


916.7 


41.5 


331 4 


76 


180.9 


129.. 


106.5 


155 


.887.0 


42. 


327-4 


77 


178.6 


130. 


105.7. 


16. 


859 -4 


42 5 


323-6 


78 


176.3 


131. 


104.9 


165 


833.4 


43- 


319 8 


79 


174-1 


132. 


104 1 


17. 


808 -."8 


43-5 


316 


80 


17! -9 


133. 


103 3 


17.5 


785.8 


4*L ' 


312.6 


81 


169.8 


134 


102.6 


18. 


763 9 


44^5 


309,0 


82 


167.7 


135. 


101.8 


18.5 


743- 2 


45- 


305-6 


83 


165 7 


136. 


101 . i 


19- 


723 -7 


45-5 


302 . 2 


84 


163.7 


137. 


100.3 


19-5 


705 t 


46. 


298.9 


& 


161.8 


138. 


99.6 
98.9 


20. 


687.5 


46.5 


2956: 


86 


159-9 


139- 


20 5 


670.8 


47- 


292.6 


P 


158.0 


140. 


98.2 


21. 


6548 


47 5 


289.4 


88 


156.2 


141. 


975 


21-5 


639.6 


48. 


286.5 
283 5 


•89 


. !54.5 


142. 


96 § 


22, 


625.0 


48.5 


90 


• 152.8 


143- 


96.1 


22.5 


6IJL.2 


49 


280.6 


9i 


151.1 


144. 


95-4 


23-, 


597-8 


49 5 


277-8 


92 


149.4 


145- 


948 


23 -5 


585-2 


50. 


275.0 


93 


147.8 


I46. 


94.1 


24. 


572.9 


50.5 


272 3 


94 


146.3 


147. 


93-5. 


24.5 


561 2 


5i 


269 6 


95 


144.7 


I48, 


,92.9 


25. 


55o.o 


51- 5 


267 


96 


143 2 


'49- 


•92.2 


25-5 


539 2 


52. 


264.4 


97 


141. 8 


150. 


91.6 


26. 


S2 !-2 


52.5 


261.9 


98 


1403 


W x i 


91.0. 


26.5 


518.8 


53 


259-4 


99 


138.9 


152. 


90.4 

8 9 ;8 


27. 


509 3 


53-5 


257 


100 


137.5 


153. 


27 5 


500-0 


54- 


254.6 


101 


136. 1 


i54 


89.2 


28. 


49* * 


54 5 


252 3 


102 


134.8 


155- 


S-7 


28.5 


482.4 


55- 


250 


103 


133-4 


156. 


88.. 1 


29. 


474 J 


55 5 


247.7 


104 


132.2 


I5 Z- 


87.5 


29S 


466 .'2 


56. 


245-5 


105 


130.9 


158. 


87 


3° 


458.3 


56.5 


242.4 


106 


129.7 


159. 


86„4 


30-5 


450 8 


57- 


241.2 


107 


128 5 


160. 


!$$ 


3»- 


443-5 


57-5 


239.1 


108 


127-3 


161. 


85-1 


3i-5 


436.6 


58. 


237 1 


109 


126. 1 


162. 


84.$ 


,32. 


429 7 


58.5 


235-1 


iio 


125.0 


l p' 


83.8 


325 


423.0 


59 


233-1. 


in 


123.8 


164. 


33. 


416,7. 


59-5 


231.1 


112 


122 7 


165 ; 


IH 


33-5 


410.4, 


60. 


229.2 


113 


121.6 


166. 


82.8 


34- 


404.5 


61. 


225 4 


114 


120 6 


167. 


82.3 
81.8 


34-5 


398,6" 


62. 


221 7 


115 


'"9-5 


168. 


35- 


392.9 


6 J' 


218.3 


116 


118 5 


169. 


81.3 


3|..5 


3f7,4 


64 


2I4.9 


117 


lT6'-5 


170. 


80.8 


3& 


381.9. 


65. 


'211. 5 


118 


171 


80.4 



And Its Appliances. 



171 



QUANTITY OF STEAM ACCOUNTED FOR BY 
INDICATOR.— Continued. 



M.E 


p 13750 


M.E. P. 


13750 


M.E. P. 


13750 


M.E. P. 


13750 


lbs 


M.E. P. 


lbs. 


mTk.p. 


lbs. 


M.E. P. 


lbs. 


M.E. P. 


172 


79-9 


193. 


71.2 


213 


645 


233, 


59-0 


173 


79-4 


I94. 


70 8 


214. 


64 2 


234. 


S l 


? 


174 


79 


195 


70.5 


215- 


63 9 


235- 


58 


5 


175 


78 5 


I96. 


70. 1 


216. 


63 6 


236. 


58 


2 


176 


78.1 


197. 


69.7 


217. 


63-3 


237- 


58 





177 


77 


6 


I98. 


69.4 


218. 


63.0 


238. 


57 


7 


178 


77, 


2 


199. 


69.0 


219. 


62.7 


239. 


57 


5 


179 


76 


8 


20O. 


68.7 


220. 


62 5 


240 


57 


2 


180 


76 


3 


20I . 


68.4 


221. 


62.2 


. 241. 


57 





181 


75 


9 


202. 


68.0 


j 222-. 


61.9 


242. 


56 


8 


182 


75 


5 


203. 


67.7 


223 


61 6 


243- 


% 


5 


^ 3 


75 


1 


204. 


67 4 


224. 


i l 3 


244. 


s i 


3 


184 


74 


7 


205. 


t.7.0 


225. 


61 1 


245- 


56 


1 


185 


74 


3 


206. 


66.7 


226. 


60.8 


246. 


55 


8 


186 


_ 73 


9 


207. 


66 4 


227 


60 5 


247. 


55 


6 


187 


73 


5 


208 


66.1 


228. 


60.3 


248. 


55 


4 


188 


73 


1 


209. 


P- 7 


229. 


60 


249. 


55 


2 


189 


72 


7 


2IO. 


65.4 


23O. 


59-7 


250 


55 





I90 


72 


3 


211. 


6 Jl 


231. 


59-5 


251. 


54 


7 


191 


7i 


9 


212. 


64.8 


232. 


59-2 


252. 


54 


5 


I92 


7i 


6 




1 











The foregoing table gives the result of the division for 
each half pound mean effective pressure, between 10 and 60, 
and for each pound between 60 and 252. 

It is a good plan to compute the steam accounted for, at 
both cut-off and the release points of the diagram ; because if 
the expansion curve should deviate much from the isothermal 
a very different result is shown at one point from that shown 
at the other. 

In many cases the extent of the loss occasioned by cylin- 
der condensation and leakage is indicated in a more truthful 
manner at the cut-off than at release. 

The constant 13750 may also be employed in a somewhat 
similar manner for computing the steam consumption of an 
engine, by the following method. 

Select any point as at D. on the expansion curve, Fig. 83, 
and draw a line from it, and parallel with the vacuum line, 



172 



Steam Engine Indicator 



until it intersects the compression line at C, then with the scale 
of the spring, (measuring from vacuum to the height of this 
line above) find the pressure of steam at such height ; then 
from Table No. 8, find the weight of a cubic foot of steam at 
that pressure. 



M.E.P. Jf. 




V- 



Fig. 83. 



Multiply 13750 by this weight of steam per cubic foot, and 
by the distance in inches, between the points C. and D. Di- 
vide the product by the mean effective pressure multiplied by 
the distance A. A. or the extreme length of the diagram. 

The result will be the number of pounds of steam con- 
sumed per indicated horse power per hour as shown by the 
diagram. 

For example : Suppose the whole length of the diagram' 
to be 3.75 inches, and the distance between the points C. and 
D, 3.10 inches, the scale of the spring 40, and the mean effect- 
ive pressure 39 pounds per square inch, the pressure from va- 
cuum to line C. D. being 30 pounds. The weight of a cubic 
foot of this steam as shown by the table No. 8 is .0755 pounds. 



And Its Appliances. 173 

-tm_ r 13750X .0755X 3.10 

Therefore -^-= ^^ — = 22. pounds consumption per 

39X3-75 F F 

indicated horse power per hour. 

The use of the constant number 13750 is based on the fol- 
lowing considerations : 

If a piston one square inch in area moves twelve inches, 
it will do work equal to one foot pound for each pound pressure 
of steam per square inch. That is, every twelve cubic inches 
of piston displacement represents one foot pound of work at 
one pound mean effective pressure ; and as twelve cubic inches 
is equal to T \± of a cubic foot, the piston must sweep a volume 

of ?3 — 13750 cubic feet per horse power per hour, when 

144 

the mean pressure equals unity ; therefore as the volume of 

steam used per horse power per hour varies inversely as the 

mean effective pressure and if the weight of a cubic foot of 

steam at the release pressure be designated by W, and the 

mean effective pressure by M. E. P. we have the formula, 

^r^- L ^ X W=the number of pounds of water consumed per 
M. E. P. r r 

indicated horse pow r er per hour, exclusive of waste by condens- 
ation and leakage ; and also makes no allowance for clearance 
and compression. 






1 74 Steam Engine Indicator 



CHAPTER XXII. 



INDICATOR TESTING DEVICE. 



In indicator practice it is frequently found that the initial 
pressure in the steam cylinder, as shown by the indicator dia- 
gram, will in some cases be from five to ten or twelve pounds 
less pressure per square inch, than the pressure in the boiler, 
as indicated by the steam guage. 

This discrepancy in pressure between the indicator and 
steam guage may arise from various causes ; such as inadequate 
size of steam pipe, also tortuous and rough passages, non- 
covered or unprotected pipes, incorrect valve setting, tardy 
valve motion, etc. ; all or any of which tend to cause an appar- 
ent difference of pressure between the indicator and steam 
gauge. 

Where such differences do exist in these pressures, the 
fault is generally supposed at first thought, to lie with the in- 
dicator, when in fact it may be due to any of the causes 
named ; or may be due to the incorrectness of the steam gauge 
itself. 

Therefore it becomes important that means be taken to 
ascertain how near the gauge and indicator agree in denoting 
the steam pressure, in order that the amount of pressure lost 
between the boiler and engine may be determined. 



>lnd Its Appliances. 



17$ 



For making such comparative tests the arrangement illus- 
trated in Fig. 84, is easily constructed, not very expensive,, 
and is well adapted for the purpose. 

It may be connected directly with the steam space of the 
boiler, or may be attached to the steam pipe in any convenient 
position. 




In making a comparative test when the device is attached 
to the steam pipe (as shown) it is best that it be done at a time 
when the engine is at rest, and the throttle valve closed in or- 
der to avoid any fluctuations of pressure that otherwise might 
exist in the pipe. 



iy6 Steam Engine Indicator 

In the matter of construction the Chamber C. should be of 
such size as to contain a considerable volume of steam, and 
such chamber may consist of an ordinary four inch cross fitting, 
with the inlet and outlets reduced to suit the size of pipe em- 
ployed. 

Steam is admitted to the system through a i inch pipe, 
and controlled by the globe valve A, and discharged as occa- 
sion requires, through the i}( inch pipe by the valve D. This 
pipe is made larger in order to facilitate the discharge of the 
volume of steam under pressure in the chamber, as quickly as 
possible. 

The top is tapped to suit the indicator cock I, which is us- 
ually made of a size corresponding to ]/ 2 inch pipe fittings. 

The bent pipe U, leading to the steam guage G, may be 
of y A inch pipe. 

The bend in the guage pipe should be extended downward 
at least four or five feet below the center of the four inch cross 
fitting; thereby securing a sufficient column of water to insure 
against overheating of the gauge above the existing medium, 
or atmosphere. 

Before preparations for any tests are made, it will be 
advisable to partly fill the gauge pipe with water ; which can 
be readily accomplished by disconnecting the gauge G, and 
pouring water into the pipe until it stands in both legs of the 
pipe about as high as the center of the chamber C. 

In preparing to make a test, attach the indicator contain- 
ing its spring, and also steam guage, in the manner shown in 
the illustration, and secure a piece of paper in the usual way 
to the drum of the indicator. Close the discharge valve D, and 
open the indicator cock I, also open communication between 
indicator, and gauge, by means of cock F. 

Now by gradually admitting steam to the chamber by the 
valve A, there will be a simultaneous advance movement of 
both the indicator pencil, and gauge hand, and which will 



And Its Applia7ices. ijj 

continue as the steam is admitted until the desired limit of the in- 
dicator spring has been reached. This is a preliminary oper- 
ation for the purpose of warming up the indicator preparatory 
to making the card. 

After the indicator and its spring has been thoroughly 
warmed, first close the valve A, and then open the valve D, 
thus discharging the steam from the chamber, through the 
open pipe into the atmosphere ; and thus lowering the pres- 
sure, and causing the indicator pencil and gauge hand to 
return each to their normal positions. 

Now with one hand, bring the indicator pencil in contact 
with the paper on the drum ; and by means of the cord E, 
(with the other hand) cause the drum to rotate a small amount, 
which in consequence results in tracing a line upon the paper, 
and which represents the zero or atmospheric line. 

Then close the discharge valve D, and slowly admit steam 
to the chamber through the valve A, and continue until the 
observed reading of the steam gauge denotes, say ten pounds 
pressure per square inch. 

Just at this point mark another line on the paper by the 
same means, (by hand) as employed in tracing the atmospheric 
line. 

Continue to mark the corresponding lines on the paper for 
each successive ten pounds movement of the gauge hand (from 
observation) until the pressure limit of the indicator spring has 
been reached. 

Close the admission valve A, and discharge the steam re- 
maining in the chamber through the valve D. 

Remove the paper from the drum, and compare the mark- 
ing with a rule or scale, on which the divisions coincide with 
pounds pressure per square inch, according to the denomination 
of the indicator spring used. 

Supposing a forty pound spring is to be used in the indi- 
cator, and assuming both the steam gauge and spring as 



178 Steam Engine Indicator 

correct ; then the marking would appear as shown at A in the 
illustration Fig. 85 for each ten pounds on the gauge, succes- 
sively from zero to eighty pounds pressure per square inch. 
But in many cases they do not agree so uniformly, as shown 
in the figure from the fact than steam gauges, and also indica- 
tor springs vary more at some pressures, than at others; 
hence, such a test enables the operator to observe the true ac- 
tion of the spring; also at what part of the marking the great- 
est variations (if any) occur, and shows that some springs 
although correct in some parts of their compression, are incor- 
rect in other parts; and also that either gauge or spring may 
show light at some pressure and heavy at another. 

If the spring registers the greater pressure according to 
its scale it is light, and if less it is heavy, provided the steam 
gauge is correct. 

This device is easily manipulated to mark a descending, 
as well as an ascending pressure, and on the same paper, and 
may be accomplished by a very gradual releasing of the pres- 
sure in the chamber, after the extreme height (to which the 
indicator spring should be subjected) has been reached, and in 
again marking the paper, upon the descent of the pencil, from 
the same readings of the gauge as was done in the ascending 
pressure. 

A comparison of this kind is both interesting and instruc- 
tive, as it furnishes the means for observing the various phe- 
nomina connected with springs in general, and in their appli- 
cation to different purposes. 

In a test of this description, and where friction exists in 
the indicator, it is found that a variation or lack of coincidence 
more or less, appears in the lines so marked ; that is, a differ- 
ence between the lines marked when the pencil is rising and 
those marked when the pencil is under falling pressure ; the 
latter failing (particularly at the higher pressures) to drop suf- 
ficiently low, as to meet the lines marked during a rising 



A nd Its Appliances. 



179 



pressure : A corresponding pressure always being denoted by 
the steam gauge at each marking up or down. 

This lack of coincidence, gradually decreases from the 
higher pressures downward until the zero line has been reached, 
and where the lines again agree. 

This is shown at B, Fig. 85, and the column marked up, 
is the rising, and that marked down the falling pressure. 

The fact of their disagreement is caused principally to 
undue friction in some part of the indicator, and might also be 



Up 



Up Down 



20 
10 \ 



80 
70 
60 
SO 
40 
30 
20 
10 

Fig. 85. 







-99 — 

70 






60 
55 
40 
30 

ao 

10 
-0 



























B 



partly due under some circumstances to lost motion in the pen- 
cil mechanism. 

Consequently the elimination of friction in the indicator to 
a minimum, is a matter greatly to be desired ; it being an im- 
portant requirement in all indicators, in order to insure accu- 
racy in the diagrams. 

Although an indicator, upon inspection may appear satis- 
factory in all respects when cold, it may become the reverse of 
this when in operation and subjected to a high temperature of 
steam ; this, application of heat, and circumstances causing 



180 Steam Engine Indicator 

unequal expansion of the metals of which the indicator cyl- 
inder is composed. 

The expansion that takes place upon being heated, varies 
in the different parts of the indicator; generally increasing 
the size of the piston to a greater extent than it does the sur- 
rounding metal ; and thereby involves a liability of the indica- 
tor piston to become sufficiently increased in size as to bind in 
the cylinder ; thus creating excessive friction, but which may 
obviously be eliminated by a slight reduction in the size of the 
piston. 

Another source of friction which often happens, arises 
from springs of imperfect construction, or out of true, causing 
when under tension, a lateral or side pressure against the 
cylinder. 

Either of these faults results in an interrupted or broken 
action in the movement of the pencil, and which is fatal to the 
accuracy of the instrument, therefore in order that perfect 
freedom of action, and that smoothness and accuracy in the 
pencil movement be attained, it is indispensable that friction in 
the instrument be reduced to the lowest degree possible. 

By the use of this device an amount of interesting and 
varied information may be obtained, pertaining to the condi- 
tion and action of springs, the variations in pressure for equal 
movement of the pencil, in showing the difference between 
a rising and falling pressure when undue friction is present, 
and also as a means of observing inaccuracies that may appear 
in any part of the mechanism connected with the indicator. 

In many cases errors arise from excessive friction of the 
indicator piston, caused by scale or grit of any description 
being carried from the pipes and other connections leading 
to it. 

If such should be suspected it will likely be detected 
(where slow speeds prevail) either by close observation of the 
pencil in its movement up and down, or by placing the finger 



And Its Appliances. 181 

at the top of the indicator piston rod, and gently follow it in 
its downward movement. 

As a matter of course the remedy is to remove the piston 
and clean. 

Sometimes with new indicators and clean pistons an un- 
usual amount of piston friction shows itself in the diagram by 
a series of very definite serrations on the expansion line just 
after cut-off, as shown in Fig. 86 the horizontal portion of the 
serrations indicating a disposition of the piston to hang at each 
of these positions in its descent. 




Fig. 86. 

In some cases of this kind it may be necessary to very 
slightly reduce the size of the piston by means of a fine crocus 
paper, or by oiling, and allowing it to run a short time, having 
first disconnected the pencil movement. 

With springs of a higher tension, that is, with stronger 
springs, the serrations resulting from the friction of a 
tightly fitting piston, will not be so apparent, and will be less 
defined, than with the lighter springs. However the difference 
in results on the diagram between a tight piston, and one fit- 
ting freely, will be, that with the former the various events of 
the stroke such as cut-off > release, and compression, will occur 



1 82 Steam Engine Indicator 

later in the stroke, owing to the tardy response of the piston 
to the variations of steam pressure. 

The fricton of a tightly fitting piston therefore will cause 
the initial pressure to be less, but the pressure along the expan- 
sion, and also the back pressure line, (on account of its tardi- 
ness) will be greater, than with the more freely moving piston. 

However the area of diagrams from each may not differ 
greatly; because the loss of initial pressure is partially com- 
pensated in the formation of the expansion line ; owing to a 
tardy piston. 

Occasionally the mean effective pressure in each may not 
differ materially, still in most diagrams that have been taken 
with an indicator in which the piston was too tightly fitted, the 
diagrams have been found to be unreliable, inaccurate, and 
misleading. 

The piston friction on an indicator may be approximately 
determined in the following manner : First allow the instru- 
ment (by a few working strokes) to become heated to a temper- 
ature coinciding with the steam pressure present; then after 
closing communication with the engine cylinder, gently 
depress the pencil lever (by hand) just sufficient to slightly ex- 
tend the spring, and then allow it to slowly return to rest. 

While in this position a horizontal line is drawn on the 
diagram. 

The pencil lever is next raised and the spring slightly com- 
pressed, and then again allowed to come to rest and another 
line drawn as before. 

The distance or space between the lines so marked is a 
measure of the sum of the total frictional resistance in both 
directions, and assuming the pencil movement without friction, 
then the whole of the error so measured is attributable to pis- 
ton friction. 

Careful attention to the lubrication of the piston, and pen- 
cil movements will conduce to smooth running, and to a certain 



And Its Appliances. i S 



extent, will prevent the tendency to stick or bind in the 
cylinder. 

Clean cylinder oil will be found a far superior lubricant 
for the piston, than the limpid oil used for the pencil move- 
ments. 



& T •% 

«/ t \W 



184 Steam Engine Indicator 



CHAPTER XXIII. 



PLANIMETERS. 



Where considerable care and attention is used the mean 
effective pressure of diagrams may be computed with a close 
approximation to accuracy, by the use and method of ordinates, 
as before described, but the operation is usually attended with 
considerable anxiety, and also becomes otherwise a rather tedi- 
ous operation in various ways with more or less liability of 
error. Therefore, where the mean effective pressure of a large 
number of diagrams is desired, and where greater accuracy is 
required, time and labor may be greatly facilitated by the use 
of an instrument termed a Planimeter, constructed and used 
for the purpose of correctly measuring the area of any irregular 
figure regardless of its outline. There are various forms of 
this instrument, some of which are so constructed that by 
moving the tracing point over the entire outline of a diagram, 
its area may be read from a graduated index wheel, its move- 
ment being relative to some fixed or zero point. There are 
others in which the reading is taken from the movement of a 
blank wheel, traversing a graduated scale, and the result is 
ascertained by noting the coincidence on the scale of some 
particular line corresponding to the edge of the wheel that has 
been selected, and made to coincide with a zero point of the 
scale; when commencing to trace the diagram. 

The instrument shown and illustrated in Fig. 87 is one of 
the former, with a graduated index wheel and vernier and 



And Its Appliances. 



represents the well known Coffin Averaging Planimeter in 
position on its board ; and which was especially designed and 
adapted to the purpose of measuring the mean effective pres- 
sure of indicator diagrams. With this instrument no calcula- 

t i o n s whatever 
are required to 
ascertain the av- 
erage pressure or 
mean height o f 
the diagram 
throughout the 
stroke of the en- 
gine, and it may 
also be applied, 
when desired, for 
measuring the 
areas of any, and 
all other irregu- 
lar figures. It is 
especially valua- 
ble where a large 
number of dia- 
grams have to be 
measured for area 
or mean effective 
pressure, either 
or both of which may be ascertained at all times 
(without any adjustment of the instrument), by a 
single passage of the tracing point around the outline of the 
figure. In consideration of the accuracy attained and the ease 
with which it is manipulated makes its use desirable in all cases 
in a single as well as in a number of diagrams, as the chances 
of error in making calculations are entirely eliminated. 




1 86 Steam Engine Indicator 

The parts of this instrument being permanently secured in- 
sures it always ready for use, without. the necessary adjustment 
to length of diagram, etc., required by some other makes, in 
order to ascertain areas and average pressures, and which gives 
only the readings of one or the other separately. This instru- 
ment measures the area and average pressure or mean height 
of any diagram or figure at the same operation, however ir- 
regular, or whatever its shape may be, just as quickly and 
accurately as if it were some regular figure, such as a square 
or rectangle. 

The Coffin Averaging Instrument proper consists of an 
arm fitted at one end with a tracing point O, and at the other 
with a hardened steel guide pin (not shown in the cut), the 
centre of which is common with the centre of the weight Q. 
Upon this arm is also mounted a graduated index wheel and 
spindle, delicately poised on hardened steel centres, thereby 
reducing friction to a minimum. The axis of said wheel being 
parallel to a line drawn from the centre of a guide pin to the 
tracing point. In close proximity to the wheel there is per- 
manently secured to the arm a graduated vernier scale and 
used in connection with the graduations of the wheel, thereby 
enabling the readings to be readily observed in small fraction- 
al parts of a square inch. The distance between the centres 
of the guide pin and the tracing pointof the arm is assumed 
to represent the length of one side of a rectangle, while the 
circumference of the graduated wheel represents its component 
or height, and if the terms of these two factors be in inches, 
the product of their multiplication will be the area of the 
rectangle of such dimensions in square inches. For example : 
In this instrument the distance between the guide pin and 
tracing point is six and one-quarter (6.25) inches, and the cir- 
cumference of the wheel two and four-tenths (2.4). correspond- 
ing to a diameter of about .764 part of an inch, then 6.25x2.4 
is equal to fifteen square inches, which will be the area of a 



A?id Its Appliances 187 

rectangle, where one of its dimensions coincides in length with 
the distance between the guide pin and tracing point, and the 
other with the circumference of the graduated wheel. The 
circumference of the wheel is therefore divided into fifteen (15) 
main divisions, each division representing one square inch area 
of the rectangle. 

Each of the main divisions are sub-divided into five (5) 
equal parts, each one representing one-fifth (1-5) or twenty 
hundredths of a square inch. The vernier scale is composed 
of ten (10) divisions, their combined linear distance being just 
equal to nine (9) subdivisions of the wheel. Therefore, as each 
subdivision on the wheel represents one-fifth (1-5) or twenty 
hundredths (20) then, accordingly the divisions of the vernier 
will represent eighteen hundredths (18) a difference of two 
hundredths (02), consequently the vernier enables the sub- 
divisions to be read to one-fiftieth (1-50) or two hundredths 
(.02) of a square inch. 

Accompanying the instrument is a nicely finished mahog- 
any board, upon which it is mounted when in use, and an 
especially prepared blank card is firmly secured to the board 
upon which the Index Wheel travels. There is also fitted to 
the board a metal grooved guide I in which the guide pin slides 
being secured therein by the weight Q. The Clips C and K 
are for the purpose of securing the card to be measured in the 
most easy and convenient position for the operator. The 
angle clip C is fixed permanently to the board with its inner 
edge in a direct line with the centre of the groove in the guide 
I. The clip K is secured to a slide that is moveable in order 
that it may be adjusted to any length of card. The guide I is 
secured by a suitable thumb screw on the under side of the 
board; said guide is shown in the cut with its end projecting 
beyond the board, which is its proper position when in use. 
The guide may, if desired, be reversed on the board which 
will bring its end even with the same, and affords a better 



1 88 Steam Engine Indicator 

opportunity of packing or laying away when not in use. In pre- 
paring to use the instrument the indicator card is first placed un- 
der the clips C and K which are so made as to admit of its be- 
ing inserted underneath and adjusted in the proper position, 
that is, with the extreme left hand end of the diagram coincid- 
ing with the perpendicular edge of the clip C, while the atmos- 
pheric line is placed near to and parallel with the horizontal 
edge of the clip. The movable slide carrying the clip K is 
then adjusted, until the edge of the clip just touches the right 
hand end of the diagram, the presure of the clips upon the 
paper serving to secure it firmly while the work upon it is be- 
ing performed. The slide to which the clip K is secured, is 
fitted so that only a slight pressure of the thumb or ringer is 
required to move it in either direction. 

The mean effective pressure of an indicator diagram being 
one of the principal factors in the computation of power of 
steam engines, hence this particular location of the diagram 
upon the board (as represented in the cut) is only necessary 
where the finding of this quantity is desired. Otherwise, in 
cases where only the area of the diagram or other irregular 
figure is needed, it may be placed in any desired position with- 
out reference to any point, and the area read directly from the 
graduated wheel. The instrument is then arranged upon the 
board with its guide pin inserted in the groove of the guide I, 
and secured therein by the weight Q. The tracing point O is 
then moved to the extreme right hand end of the diagram, 
where the line is in contact with the clip K (as shown at D). 
Here make a slight indentation in the paper, by pressing the 
thumb against the top of the tracing point; this gives the start- 
ing point from which to trace around the diagram 

The zero mark of the graduated wheel is then turned and 
made to exactly coincide with the zero mark on the vernier. 
In commencing operations the direction in which the diagram- 
should be followed by the tracing point is ; first along the back 



A nd Its Appliances, 1 89 

pressure and compression lines, thence returning by way of the 
expansion curve to the starting point. The only object in 
tracing in this direction being that the main divisions on the 
wheel are numbered towards the left from the zero mark, and 
consequently in this direction any movement of the wheel is 
recorded in regular order, as 1, 2, 3, etc., whereas, if the diagram 
is traced in the opposite direction, the reading will be the re- 
verse of this, as 14, 13, 12, etc., and, although the circumfer- 
ential movement of the wheel would be precisely the same in 
either case, the only consequence of tracing the diagram in the 
latter direction would be the inconvenience of reading the 
areas. 

In the measurement of indicator diagrams, for mean effec- 
tive pressure, no attention whatever need be given to reading 
the areas. After the tracing point has made a complete circuit 
and again reached the starting point, it is then moved upward 
along the edge of the clip K until the zero mark of both the 
wheel and vernier coincide. Another slight indentation is 
then made at this point, (as shown in the cut at A). The dis- 
tance between these two indentations (D and A) represents the 
average height of the card, and also, if this is measured with a 
scale corresponding in pounds to the denomination of the 
spring with which the diagram was taken the said measure- 
ment will be the mean effective pressure of the diagram in 
pounds per square inch, according to the spring and scale used. 

Where two diagrams are taken on the same card it is ad- 
visable to measure and find the average pressure separately ; 
for the purpose of comparison with each other. By the use of 
this instrument all imperfections or irregularities whatever in 
the outline of the diagrams whether to be added or subtracted, 
are accounted for, and the final results given exact. For in- 
stance, where a loop is formed in the diagram (as in Fig. 62) 
caused by the expansion line crossing the atmospheric line 
early in the stroke, and running below to the end, thereby 



190 Steam Engine Indicator 

dividing the diagram into two distinct parts, its outline should 
be traced in the same manner as is done in any well formed 
diagram, as the principle upon which the instrument is con- 
structed, enables it to perform the operation of addition or sub- 
traction with the greatest exactness and will consequently sub- 
tract the effect of the said loop from the positive part of the 
diagram and the reading of the instrument after the diagram 
has been traced, will give the net average pressure per square 
inch throughout the stroke. 

Where the instrument is used to measure the area of any 
figure, it is only necessary to select a starting point. Adjust 
the zero marks on the wheel and vernier to coincide, and trace 
around the outline of the figure, then its correct area will be 
found from an observation of the number of main divisions, 
and subdivisions of the wheel that have passed beyond the 
zero mark on the vernier. 

For example : Suppose upon noting the number of main 
divisions of the wheel that have passed the zero mark of the 
vernier,- we find the largest figure to be three (3) which will 
represent inches, and the number of sub-divisions that have 
also passed the zero mark of the vernier, to be four (4), each 
subdivision representing one-fifth (1-5) or twenty-hundredths 
(.20) of a square inch, and the number of the division on the 
verneir which exactly coincides with a division on the wheel to 
be two (2), each representing two-hundredths (.02) of a square 
inch, therefore the reading taken from the instrument in this 
position will be 3~f-(4X .2o)-f-(2X .02)= 3.84 square inches, as the 
area of figure. This instrument being of careful and delicate 
construction, should be handled with the greatest care and 
kept perfectly free from any matter that might interfere with 
the movement of the wheel ; thereby insuring accurate results. 

To a great many users of the Averager or Planimeter, 
shown and described in Fig. 87, it may be considered a fact 
that the reason and principle upon which its accuracy is based, 



And Its Appliances. 191 

in the measurement of the area of any irregular figure, is, to a 
certain extent, shrouded in mystery; but nevertheless it is 
well-known that a comparison of its readings, taken from 
figures of known areas, prove its reliability and correctness, 
and can under all circumstances be depended upon for correct 
results ; hence, a study of the theory of its operation may be 
interesting to many. 

The manipulation of the instrument being easily per- 
formed, as before described, and its theory quite simple, we 
shall endeavor to make clear and explain why, by simply 
passing the tracing point around the outline of a given figure, 
its exact area will be denoted on the registering wheel. In 
attempting this we shall leave out, wherever possible, the use 
of the higher mathematics usually employed in connection 
with a discussion of the subject, and also shall first consider 
the instrument in its application to the measurement of areas, 
and which consideration will also apply in principle to all other 
planimeters. Although the principle is simple, still it is 
necessary for the reader not conversant with it, to follow 
closely the explanation in order to become familiar with the 
peculiar movements and actions of the registering wheel. 

In Fig. 88 the outline A, Ai, C, D and A3, is assumed 
for our purpose to represent an indicator diagram, the expan- 
sion curve being shown in dotted lines. The point A on the 
diagram is selected as the starting point from which to trace 
and consider the figure. Probably a better idea may be had, 
by first confining our study of the subject to a part of the 
diagram ; that is, the area of .the square inclosed by the lines 
A, Ai, A2 and A3. The line A1-B1 represents the arm of the 
instrument, and shows its position after the tracing point has 
been moved horizontally away from the starting point A to the 
position at Ai. This line (A1-B1) may be assumed to be a 
small round rod, the end (Bi) being guided to always move in 
a straight line, as shown by dotted line from Bi to B3 ; while 



192 Steam Engine Indicator 

the end (Ai) carrying the tracing point is free to be moved in 
any direction, and to any point of the diagram. This arm or 
rod is also shown here as the axis of the registering wheel W, 
and is represented in this way for the purpose of simplifying 
matters in the way of its demonstration, and because the final 
results of the registering wheel W, in having its axis coincident 
with the arm A1-B1, will be precisely the same as though its 
axis was located at a distance from, and parallel to, a line 
drawn between the tracing point Ai and guide pin at Bi ; 
(this latter construction being that of the instrument repre- 
sented in Fig. 87). In the diagram the four positions of the 
registering wheel are shown at Wo, W, Wi and W2, when the 
tracing point is respectively at each corner of the square or 
rectangle A, Ai, A2 and A3. 

Suppose the tracer to be at the starting point A — the arm 
then coinciding with line A-B, and the registering wheel at 
Wo ; now, any movement at the tracing point up or down on 
that line will simply cause the wheel to slide in the same 
direction, but without causing any rotation of it, because its 
axis is coincident or parallel to said line ; hence, any move- 
ment of the wheel in a direction parallel to its axis will not 
cause rotation. 

If, now, the tracing point be moved to the right, in a hori- 
zontal direction, until the arm is in the position A1-B1, then 
the wheel has moved from Wo to W, and has revolved a 
certain distance at its periphery ; the amount depending upon 
the degree of the angle formed by its departure from the 
starting point, or line A-B ; but, any consideration of the amount 
of this movement, as a factor in the case, is wholly unnecessary, 
because all motion imparted to the wheel by its departure from 
the line A-B is always exactly cancelled (in whatever direction 
it may return) on arriving at the starting point. 

Now, consider the action of the wheel in an assumed down- 
ward movement of the arm, from its position A1-B1 to a 



And Its Appliances. 



193 



position A2-B2, then the area swept over by the arm is the 

space A1-B1, A2-B2, 
which is exactly equal 
in area to that [of the 
square, or rectangle A, 
A 1 , A2 and A3 , because 
they both have the 
same base, and between 
the same parallels. 
The result of this move- 
ment of the arm will cause the register- 
ing wheel to move from W along the 
dotted line to the position Wi. The 
wheel being in contact with the paper, 
and the direction of its movement from 
' W to Wi, at an angle with its axis, will 
consequently cause it to revolve while being 
moved downward to Wi, and the amount 
of this motion at its periphery will be re- 
presented by the line W-N, which is the sine 
of the angle W, Wi, N, with Wi-W as the 
radius of the circle ; consequently, by knowing 
this angle, the length of its sine can be found 
from a table of sines, in which their lengths 
are given for any angle, the radius being 
unity. Suppose, for example, the angle formed 
between the arm A2-B2, and the vertical line 
of movement of the wheel from W to W 1 , to 
be one of 18^3 degrees, and that the vertical 
distance traversed by the wheel to be two (2) 
inches ; then from a table we find the sine for 
that angle to be . 32 in terms of inches, at unity. 
Therefore, if this be multiplied by the verti- 
cal movement, two (2) inches (. 32 X 2 = .64 in.), 




SO 



*aj 



H 

• / 

C\xV WI 

b 1 



1 



BiQ 



Fig. 88. 



this product will be the length of the line W-N. 



194 Steam Engine Indicator 

The rotary motion, therefore, that has been imparted to 
the periphery of the wheel (by being in contact with the paper 
over which it runs), in moving from W to Wi, is equal to the 
length of the line W-N, and the final result in the readings are 
precisely the same as though the wheel was first rolled in the 
direction of its rotation upon the line W-N, and then without 
rolling moved down the line A2-B2, coincident with its axis to 
Wi ; hence, this distance (W-N) if multiplied by the length of 
the arm A1-B1 (W-Nx A1-B1), is equal to the area of the space 
passed over by the arm, and is also equal to the square or 
rectangle A, Ai, A2 and A3, for the reason before stated, both 
having the same base, and between the same parallels. 

Suppose now the tracing point to be moved from its posi- 
tion A2 to A3 ; in doing this the wheel will have moved from 
its position Wi to W2, and revolved at its periphery an amount 
exactly equal to that which it revolved in being moved from 
A to Ai. Therefore, as the wheel has revolved through the 
same angle in both cases, but the motion being in opposite 
directions, will thereby cancel each other, and, as a conse- 
quence, leave no positive results on the registering wheel. 

In moving upward from A3 to the starting point at A, the 
wheel will not revolve, because this movement is parallel to 
its axis. 

From a careful consideration and study of the matter, the 
following facts may be deducted and readily observed: — 1st. 
That all movements of the tracing point that are in a direction 
parallel to the axis of the wheel, will not cause it any revolu- 
tion. 2d. That all revolution of the wheel caused by a de- 
parture of the tracer from the starting point A, will be exactly 
cancelled on its return to that point. 3. That the only perma- 
nent record remaining on the wheel (after tracing the diagram), 
is derived entirely from vertical movements of the tracer rela- 
tive to the starting point A, the amount of its revolution 
depending upon the angle formed by the arm with the line 



And Its Appliances, 195 

A-B, together with the vertical distance passed over by the 
tracer. 4th. That the amount of revolution of the wheel is 
always equal to the sine of the angle (formed by its axis with 
the direction of its movement), multiplied by the distance of 
its vertical movement. It also becomes evident that any 
departure of the tracer Ai from the starting point A, is pro- 
portional to the sine of the angle so formed, multiplied by 
the length of the arm A1-B1. Supposing this angle to be one 
of 187^3 degrees (the same as the previous example), the sin 3 
of which at unity is .32 inches, and the length of the arm 
A1-B1 to be 6.25 inches, then (.32x6.25 = 2 inches), the dis- 
tance of the tracer's departure from A. This product, then, 
if multiplied by any vertical movement of the tracer, is equal 
to the area corresponding to such movement. 

If in place of moving the tracer to Ai it had been stopped 
at the point 4, and moved down the line to 5, and thence 
through A3 to the starting point A, the area of this rectangle 
recorded on the wheel would be just one-half that of A, Ai, 
A2 and A3, because this angle is proportionately one-half of 
the former, thereby making it more acute, and consequently 
its sine would also be only one-half. The effective rotary mo- 
tion of the wheel in this case is derived entirely from its verti- 
cal movement along the line from 4 to 5. Therefore by apply- 
ing the rule (A 1.B1 X sine of angle X vertical movement = 
area), it will be found that the area of the latter is only one- 
half that of the larger rectangle. 

We may now consider the whole of the diagram. Fig. 88, 
including the dotted curve line Ai, C. ; and in doing so it must 
be understood that Avhatever has been said in reference to the 
larger rectangles, is equally true of any, and all, others that 
may be inscribed within its extreme outline ; (however numer- 
ous, whatever their size, and wherever located). If in addi- 
tion to the larger rectangles we inscribe smaller ones, num- 
bered 1.2, and 3 in the diagram, and from the starting point 



196 Steam Engine Indicator 

A, carry the tracer around their extreme outline, so as to in- 
clude their measurements; it will be found on returning to the 
starting point, that the reading on the wheel will be increased 
by an amount just equal to the combined areas of the smaller 
rectangles 1-2 and 3, (over the readings taken from the larger 
ones contained in the square A-A1-A2 and A3 :) and such read- 
ing will be approximately the area of the diagram. 

Other additional smaller rectangles may still be inscribed 
in the spaces adjacent to the dotted curved line ; (said space 
yet remaining unaccounted for in the reading;) And if these 
smaller rectangles should be made sufficiently numerous, and 
measured separately, by passing the tracer, in turn, around 
the extreme outline of each, without removing from the paper, 
the wheel would mechanically add the area of these rectangles 
together, and on the return of the tracer to the starting point 
A, the reading of their combined sum would be exactly equal 
to the area of the whole diagram ; and which will also be equiv- 
alent to the reading that would appear on the wheel after pass- 
ing the tracer around the outline of the diagram, including the 
curved line Ai, C. 

Therefore it will be seen that as the horizontal movements 
of the tracer, over the lines of any rectangle, cancel each other, 
while only vertical movements relative to the starting point A, 
leave any permanent record on the wheel, the results will be 
precisely the same as though the tracer had simply moved over 
the actual extreme outline of the diagram 

As the area of any rectangle or parallelogram, is equal to 
the product of its length multiplied by its vertical height, it is 
readily seen, that after passing the tracer once around the out- 
line of any figure, (regular or irregular:) its exact area will be 
denoted by the number of divisions of the wheel that have 
passed the zero mark on the vernier ; consequently the neces- 
sary height of a rectangle of the same length, to contain the 
same area may be determined by moving the tracer upward along 
the clip K. until the same number of divisions have returned ; 
and the zero marks on the wheel, and vernier again coincide, 



And Its Appliances. 197 

(as mentioned in the description of the instrument in Fig - . 87), 
which point will be the average height of a parallelogram, con- 
taining exactly the same area as the figure traced. Therefore 
in case the figure traced be an indicator \ diagram, such point 
must be its average height, because it is the height of a rec- 
tangle of the same length, and same area as the diagram. Con- 
sequently if this average height be measured by the scale of 
the spring with which the diagram was taken, the units of the 
scale will show the mean effective pressure in pounds per square 
inch throughout the stroke of the engine without any compu- 
tation whatever. 

The number of parts into which the circumference of the 
wheel may be divided; can be 10-15-20 or any other convenient 
number; the only requisite being, that the circumference of 
the registering wheel shall be so proportioned that one com- 
plete revolution on its axis, would cause it to roll over the 
paper an amount, such, that if this distance was multiplied by 
the length of the tracer arm, that their product will be equal to 
the area of a rectangle containing exactly some whole number of 
square inches; (suppose for example fifteen:) now if the cir- 
cumference of the wheel be graduated into the same number 
of divisions, and numbered accordingly from one to fifteen, 
then each division on the wheel will represent one square 
inch ; and the area of any figure, after the tracing point has 
passed around its outline, will be indicated in square inches, 
vaccording to the number of divisions of the wheel that have 
passed a given point. We again mention the necessity of 
handling the instrument with great care in order to obtain the 
most accurate results , never allowing the contact edge of the 
registering wheel to become indented in the least, keep perfect- 
ly free from rust or deposit of any kind, and a good plan, is to 
pass a thin piece of paper between the wheel and vernier to 
remove any particles of dust that may accumulate and destroy 
the free action of the wheel ; see that the spindle runs easily, 
and freely between the centres, and practically without end 
play ; and care must also be taken to prevent the tracer arm 
from getting bent or in any way out of shape. 



198 



Steam Engine Indicator 



The Anisler Polar Planimeter. Illustrated in Fig. 89 
is another device for measuring diagrams : This instru- 
ment does not give the mean effective pressure directly, 
but it determines the area of the diagram, and from 
this area the mean effective pressure is computed in 

the manner described. It con- 
sists of the two arms, A and 
D, and the measuring wheel, 
C. To operate it, a piece of 
smooth, hard paper is laid on 
the table, and the instrument 
placed upon it, with the needle 
point, A, pressed into the board. 
This point serves as a centre 
about which the apparatus is 







^ 







D \yiA 




%&) 




V 

"^ Jj B 


J 













Fig. 89. 
turned. The indicator card is laid under the tracer, 
B, and held either by tacks, which fasten it to the 
table, or what is quite sufficient, by the pressure of 
the fingers. The tracing point is set on the line of 
the diagram — say near the middle of the steam line — and a 
slight indentation made in the paper, to serve as a starting 



A nd Its Appliances. 1 99 

point. The graduated wheel is set at the zero mark. The 
tracer is then moved over the line of the diagram in the di- 
rection of motion of the hands of a watch, finally making a 
complete circuit, and returning to the starting mark. The 
number of divisions and fractions of a division shown on 
the wheel at the point opposite the stationary zero mark, indi- 
cates the area of the diagram traced. The wheel has ten main 
graduations, each of which represents one square inch of area. 
Each main division is subdivided ten times, and each subdi- 
vision represents one-tenth of a square inch of area. A 
stationary vernier scale E is placed beside the graduated edge of 
the wheel, and serves to indicate the smaller fractions, viz., 
hundredths. To read the vernier, the eye is run along the 
stationary scale till a line of division is found which is just 
opposite a division on the wheel. The number of the division 
on the vernier, reckoned from the zero mark, is the number of 
hundredths sought. If, for example, the reading of the area 
is two main divisions on the wheel, and four of the subdivisions 
and the line of coincidence on the vernier is number seven 
reckoned from zero, the area sought is 2.47 sq. in. 

To reduce this to mean effective pressure, two perpen- 
dicular lines are drawn, one through each terminal point of 
the diagram, and the length of the diagram is measured by 
measuring the distance between these two perpendiculars. 
Suppose this distance is 3.78 in., and suppose the number of 
the spring employed is No. 40. Then the mean effective pres, 
sure is found by dividing 40 by 3.78 and multiplying the result 
by 2.47. Making this computation the mean effective pressure 
sought is 26. 13 lbs. per sq. in. 

In working the Polar Planimeter, care must be observed 
to place the diagram so that the two arms are not brought too 
near each other at one end of the course, nor yet carried too 
far apart at the other end. At a point midway between the 
two extremes the two arms should lie about perpendicular to 
each other. 



200 Steam Engine Indicator 

As an example of the manner of computing the horse- 
power of an engine, suppose an engine has a cylinder 1 5 inches 
in diameter, a piston rod 2J^ inches in diameter, a stroke of 
2]/ 2 feet, running at a speed of 135 revolutions per minute. 
Suppose the indicator diagrams show a mean effective pressure 
of 36 lbs. per square inch, this being the average of the indi- 
cations at the two ends. The area of the cylinder to be used 
is the net area obtained by deducting one-half the area of the 
rod. The area of a cylinder 15 inch in diameter is 176.71 
square inches. 

One-half the area of a rod 2]/ 2 inches in diameter 2.45 
square inches. The net area to be used in the computation is 
176.71 — 2.45=174.26 square inches. The speed in feet per 
minute is 135x2^x2 = 675 feet. The horse-power developed, 
therefore, is 

36x174.26x675 4,234,518 

= ■ " ~z=. \2o.X Jti. Jr. 

33,000 33>ooo 

That is 
M.E.P. X net area of cyl. in sq. ins. X piston speed in ft. per min. 

33,000" 
When the engine has more than one cylinder, the power de- 
veloped in each cylinder is computed in the manner given, and 
the results added together. 



I 



And Its Appliances. 



201 



CHAPTER XXIV. 



COMPARISON OF DIAGRAMS FROM THROTTLING AND 
CUT-OFF ENGINES. 



The following diagrams in this chapter were taken from 
what originally was, (when new) a pair of side by side non- 




// ^&£o>>zje^ 



Fig. 91. 
condensing throttling engines, and connected to the crank 
shaft at right angles, or quartering. 



202 



Steam Engine Indicator 



After running in this manner for some time it was deemed 
advisable, and also as an experiment, to convert the valve 
motion of one of the pair into a special automatic cut-off valve 
gear in order to use the steam expansively on one engine, and 
throttling on the other. 

This alteration of the engine being completed, the dia- 
grams both in Fig. 90 and Fig. 91 in connection, were taken 
to show the extreme range of this new valve gear. 

22a / &&<>&&»<? 




Fig. 92. 








Fig. 93. 

The diagrams from Fig. 92 to Fig. 103 inclusive, are fac- 
similas of diagrams taken in pairs, after this alteration had 
been made on the engine ; having one cylinder throttling, and 
the other with automatic valve gear, and were taken to illus- 
trate the difference in the two systems of government at diff- 
erent loads ; the data of the engine being as follows : 



And Its Appliances. 



203 



AUTOMATIC ENGINE 

Dia. of Cylinder, 1 5xV i n - 

" " Piston Rod, 2}i " 
Length of Stroke, 42 " 
Revolutions per min. 60 

Piston speed " " 420' 

Scale of Spring, 40 



THROTTLING ENGINE 

Dia. of Cylinder, 15^8 in. 
" " Piston Rod, 2}i " 
Length of Stroke, 42 " 
Revolutions per min. 60 

Piston speed " " 420' 

Scale of Spring, 40 



Thus giving a value of the engine constant on the auto- 
matic side of 2.275, and of the throttling side 2.334, indicated 
horse power, for each pound of mean effective pressure, at a 
speed of 60 revolutions per minute. 




Fig. 94. 







Fig. 95. 

In calculating the horse power from the diagrams, the 
factor that has been used to represent speed has been the 
actual number of revolutions of the engine, at the time each 
diagram was taken. 



204 



Steam Engine Indicator 



The mean effective pressure was obtained by trie use of a 
planimeter, and the steam or water consumption, computed 

by the formula A T p xM E p that is > h Y dividing the 

constant 859375, by the volume of the steam at absolute term- 
inal pressure, multiplied by the mean effective pressure in 
pounds per square inch of the diagram ; the quotient being the 
number of pounds of steam or water consumed per hour per 
each indicated horse power developed by the engine. 




Fig. 96. 



/v^: y<T sV{, £.!? 




Fig. 97. 

In the latter calculation however, no allowance has been 
made for compression and clearance ; the rule for making such, 
allowance being described in connection with Fig. 77, Chapter 
XXI 

These diagrams were selected from a large number, with 
two objects in view ; first to show the different forms or outlines 
of the pressure areas between the automatic, and throttling 



And Its Appliances. 



205 



system of governing, from pairs of diagrams of approximately 
the same horse power ; and second, to show the relative rates of 
water or steam consumption of each, in pounds per horse 
power per hour. 

In addition the diagrams from the automatic side also 
show that the minimum amount of steam consumption (and 




Fig. 98. 



3ZoM <^L*&&^? 




Fig. 99. 

consequently the greatest economy) occurs in diagrams No. 5, 
Figs. 100 and 10 1, where the cut-off takes place at about 
twenty-two hundredths of the stroke, corresponding to about 
4.57 ratio of expansion, and to very nearly the generally con- 
sidered most economical point of cut-off in automatic engines 
working at a steam pressure of from 60 to 75 pounds pressure 
per square inch. 



206 



Steam Engine Indicator 



By reference to the diagrams from either the automatic 
or throttling- engine it will be observed that a gradual decrease 
in the water consumption takes place as the power developed 
by the engine increases, or, as in case of the automatic engine, 
when the cut-off takes place later in the stroke. 

The minimum consumption appears to have been reached 



/CO.cS? CtocA^nri^z&e''* 




Fig. ioo. 







Fig. ioi. 

in either case, in the diagrams Nos. 5, and it will be seen that 
in all diagrams on either side whether developing more or less 
power, that an increase in the rate of water consumption in- 
varibly takes place. 

In these diagrams the economy of the automatic cut-off 
engine, over that of the ordinary throttling system is very 



And Its Appliances. 



207 



fairly exhibited, and shows the relative economy that might 
be expected from the automatic, under ordinary circumstances, 
over that of the throttling system of regulation. 

The outlines of the various diagrams of each system are 
fair representations of what ought to be expected from an en- 
gine with properly designed valve gear, and with evenly and 
accurate adjustments of the same. 




Fig. 102. 







Fig. 103. 
It must be understood that the diagrams here presented 
are not intended, or claimed, as representing the highest effi- 
ciency and economy obtainable, but are only given from actual 
ordinary practice, in order to be able to make an interesting 
comparison between the two systems of regulation. 



208 Steam Engine Indicator' 



CHAPTER XXV. 



ECONOMY OF EXPANSION. 



As regards trie economy of expansion it will be found by 
reference to the Table No. 8 on the properties of saturated 
steam that the weight of a given volume of steam varies very 
nearly in proportion to its pressure that is, a cubic foot of steam 
at 60 pounds pressure weighs approximately twice as much as 
the same volume at 30 pounds pressure. 

A given weight of steam represents the same weight of 
water that must be evaporated to produce it, consequently the 
lower the terminal pressure at the end of the stroke in a given 
cylinder the less will be the amount of water exhausted as 
steam ; and as the measure of the work done in the cylinder by 
the steam, is proportional to the mean effective pressure, it 
becomes evident that economy in the use of steam in an en- 
gine, consists in getting a high mean effective pressure, in 
connection with a low terminal pressure. 

This can only be accomplished by cutting off the supply of 
steam, at a time when the piston has only completed a part of 
its stroke, and by that means obtain an additional amount of 
work from the expanding steam to the end of the stroke. 

Suppose in a steam cylinder using steam at 100 pounds ab- 
solute, the steam be cut off when the piston has moved one- 
fourth of its stroke, then the mean pressure calculated accord- 
ing to the rule in Chapter 1 8 will be almost 60 pounds ; and 



And Its Appliances, 209 

this is obtained by using only one-quarter of a cylinder full of 
steam ; whereas if the entire cylinder had been filled the mean 
pressure would have been only 100 pounds, with an expendi- 
ture of four times the quantity of steam used as when cutting 
off at one-quarter stroke. 

This indicates the direction in which a saving is effected ; 
but in practice however, condensation in the cylinder, and 
other causes prevent this full theoretical gain from expansion 
being realized ; at the same time however the gain from this 
source is an important one. 

Therefore from what has been said in this connection it 
would be natural to expect, in considering diagrams from first- 
class cut-off engines, to find the initial pressure of the diagram 
high, as compared with the boiler pressure, also with straight 
or fairly straight steam lines, and sharp cut-off ; because these all 
tend to bring about both high mean effective, and low terminal 
pressure ; also whatever tends to make the terminal pressure 
higher than it should be, represents waste of steam. 

Economy of High Pressure. It is a well established fact that 
the use of steam of a high pressure tends to greater economy 
in the engine ; the reason for which is simply as follows : 

Suppose in this case an engine working without expansion, 
and in order to simplify the matter, assume that there is no 
clearance. Assume also the engine to be working non-con- 
densing, with an absolute back pressure of 1 5 pounds, or three- 
tenths above the atmosphere. 

If steam of 20 pounds absolute pressure is used in the cyl- 
inder, the mean effective pressure on the piston is 20—15 = 5 
pounds. 

If the piston has a total displacement of one cubic foot, 
then we are using one cubic foot of steam, of a pressure of 20 
pounds at each single stroke of the piston. 

In the Table No. 8 on the properties of saturated steam, 
the weight of a cubic foot of steam of this pressure is found to. 



210 Steam Engine Indicator 

be .0511 pound, and the heat units per pound 1 183. 5 ; hence 
the cubic foot of steam from which the mean effective pressure 
of 5 pounds has been obtained, contained 1 183.5 X .0511 = 60.47 
heat units. 

Now instead of steam of 20 pounds pressure, suppose 
steam of 100 pounds absolute pressure be used: Then the 
mean effective pressure would be 100— 15 = 85 pounds. 

The weight of a cubic foot of steam of 100 pounds pressure 
is .2350 pounds and one pound contains 12 13.8 heat units. 
Then as before 1213.8X .2330=282.8 heat units used. 

In the first case 60.47 heat units have been used, equal to 
60.47-^5=12.09 heat units for each pound mean effective 
pressure; whereas in the second case 282.8-^85 = 3.32 heat 
units for each pound mean effective pressure have been used. 

This great difference and discrepancy in the two instances, 
arises from the fact that the greater part of the total heat of 
the steam still remains in it at the pressure of the exhaust, (15 
pounds) and all of this heat is entirely lost with the exhaust 
steam. 

The only heat that can be converted into useful work, is 
the quantity that is added above exhaust pressure ; therefore 
it becomes apparent that a greater per cent of the total heat 
can be made available, as the pressure increases. 

From this it must be clearly understood, that a large pro- 
portion of the heat that enters into the steam used in a steam en- 
gine is requisite in order to raise it to the pressure at exhaust ; 
(15 pounds), a pressure at which no zvork can be utilized from it. 

The diagram Fig. 104 fairly illustrates the economy of the 
use of high pressure steam in a cut-off engine. 

The full lines of the figure represents an actual diagram, 
and above it the shaded portion has been drawn by hand to 
show precisely as if the whole of the diagram had been taken 
at a higher steam pressure. 



And Its Appliances. 



211 



The pressure of the steam at the end of the stroke, or 
after having" performed all of the work there is in it, is not 
changed ; as the terminal pressure T remains the same : hence 
we conclude that as far as we can judge by the diagram, the 
work represented by the shaded portion could be done without 
additional expense. 

This is on the assumption that steam expands according to 
the Mariotte law, but if the result were calculated from Table 




Fig. 104. 

No. 8 (properties of saturated steam) it would be somewhat 
different, but we have no positive assurance that it would be 
any more correct ; therefore for all practical purposes, this 
presentation of the subject should prove acceptable. 

There is a point however where it is the reverse of econom- 
ical to run at very high pressures, and that is when the load 
on the engine is so light, and cut-off so short, that the steam 
expands below the atmosphere, and thereby forming a long 
loop in the diagram as illustrated in Fig. 54 and 62. 



212 Steam Engine Indicator 

In such cases the engine is running- a portion of each stroke 
on the momentum of the moving" parts. 

Where this occurs it is better to reduce the boiler pressure 
until expansion shall come quite down to, but not below the at- 
mosphere. 

In such an instance a considerable advantage is realized by 
reducing the speed of the engine ; as the resistance of the atmos- 
phere must be overcome in running an underloaded, as well as 
in a heavily loaded engine ; therefore by reducing the speed this 
factor is made less, and on lightly loaded engines becomes a 
considerable percentage of the total power; this percentage 
decreasing in extent as the engine is more heavily loaded, 

In connection with losses from having under loaded en- 
gines, is the fact also, that the friction of the engine, conden- 
sation, etc., are all present almost regardless of the load, and 
always appear in a greater proportion in light, than in heavy 
loads ; therefore the final expense is decreased when running 
at a slower speed ; as there is a better opportunity to secure a 
later cut-off, since the power being the same, with reduced 
speed, the mean effective pressure must be proportionally in- 
creased . 



#i i Mr 

m& -33r- ^^ 



d nd Its Appliances. 2 1 3 



CHAPTER XXVI 



THE POINT OF CUT-OFF. 



It must not be understood, (in reference to steam expan- 
sion) that the higher the grade or ratio of expansion, the 
greater is the economy, because, quite the reverse may often 
happen, as the results in practice are greatly modified in vari- 
ous ways by other considerations. 

Consequently the most economical point of cut-off will 
vary in different types of engines, in accordance with the 
special conditions, and circumstances to which each may be 
subjected ; such as high or low initial pressure, condensation 
of steam in the cylinder, different methods of jacketing and 
superheating, amount of backpressure and compression, incor- 
rect adjustment of the valves, also a size of engine that is not 
adapted to the work, etc. ; any or all of which necessitates a 
change more or less of the point of cut-off, in accordance with 
any particular condition, in order that the greatest efficiency of 
the engine may be realized. 

Initial Pressure. In engines with an early cut-off, and 
where a high rate of expansion prevails, the mean or average 
pressure throughout the stroke must necessarily be low ; and a 
low mean pressure, for a given power necessitates the use of a 
larger engine. 

Also a high rate of expansion leads to a low terminal pres- 
sure, and to expel the steam from the cylinder after it has 



214 Steam Engine Indicator 

performed its work, will require from one to three pounds 
pressure above the atmosphere ; therefore if the rate of ex- 
pansion be such that the terminal pressure falls below this, 
the expansion is excessive, and the reverse of advantageous. 

In non-condensing engines the lowest possible terminal 
pressure coincides with the pressure of the atmosphere, or 
about i4 T V pounds per square inch absolute; but 18 poinds 
may be considered as the lowest pressure to which steam can 
be expanded to advantage ; and where the exhaust passages 
are small and tortuous, or where the exhaust steam contains 
considerable moisture, a still higher terminal pressure will be 
more economical. 

In condensing engines, the temperature in the condenser 
is usually about ioo degree Fah., and which corresponds to a 
pressure of very nearly one pound to the square inch ; but the 
presence of air in the condenser generally prevents the pres- 
sure falling below two pounds per square inch. 

From three to four pounds is the more usual and .may be 
considered as the lowest advantageous final pressure, to secure 
the best economy. The highest advantageous rates of expan- 
sion with jacketed cylinders appear in practice to be between 
twelve and sixteen; but in unjacketed or exposed cylinders, 
the limit of advantageous expansion is much below the lowest 
of the rates mentioned. 

The principal cause of the discrepancy between the theo- 
retical, and actual economy, is in the amount of heat lost in 
changing the water in the cylinder from a heated liquid state, 
to the condition of steam; most of this heat passing out 
with the exhaust steam, either into the condenser or the atmos- 
phere. It has been fairly well demonstrated by frequent tests, 
that the most favorable point of cut-off, in a simple non-con- 
densing engine, is usually about one-fourth stroke, when using 
steam of from 80 to 90 pounds per square inch initial pressure. 



A nd Its Appliances. 2 1 5 

Where the cut-off is earlier than this a greater per cent of 
loss is induced through cylinder condensation ; and where the 
cut-off takes place later in the stroke there is also an increase 
of loss, from the fact that the steam is exhausted and lost while 
yet at a considerable pressure. 



Fig. 105, 

Fig. 105 is a fair representation of an indicator diagram 
from an engine working under the favorable conditions men- 
tioned. 

The results of some recent experiments on a 17 by 30 inch 
stroke non-condensing double valve engine by Prof. J. E. 
Denton, to determine the relation of steam consumption to 
point of cut-off is illustrated by the graphical diagram Fig. 106. 

The line A. B. represents the stroke of the engine, which 
is equally divided into tenths and twentieths, to denote the 
various points of cut-off in fractions of the stroke, or periods of 
admission of steam to the cylinder. 

From each of these fractional parts of the stroke perpen- 
dicular lines are erected, and also above these points are hori- 
zontal lines laid off 1-5 of an inch apart; each representing 4 



2l6 



Steam Engine Indicator 



pounds, or a scale of 20 pounds per inch ; being the actual 
pounds of water used per horse power per hour. 

Through these lines three curves are plotted, being the 
result of experiments at various points of cut-off, and boiler 
pressure by which the change in the rate of water consump- 
tion, corresponding to changes in point of cut-off, (as well as 
changes in boiler pressure) are readily observed. 











1 


































60 


















































\ 










































\ 


























y 








1 








\ 


















v\ |r S 


f» 
























V 


•«■. 












5° 


* 














40 




\ 








































\ 




















1 ( 


, "ft 


v. 
















\ 




















6^ 


>t> 






















\ 
























































so 


llri 


■J± 


I?. 


















SO 




















































































































































































































Cc 


•T- 


OF* 


T t 


v r 


■IAC 


no 


KS 


or 


Sr 


9Qf 


:£. 

















A 



JB 



0.1 0.2 0.3 CHI 0.5 0.0 0? 08 0.3 LOO 

Fig. 106. 
The three curves shown in the diagram corresponds to 90, 
60, and 30 pounds boiler pressure respectively per square inch, 
and the curves were constructed by locating points as a result 
of tests in each case at different rates of cut-off. It will be 
clearly seen that the curve corresponding to 90 pounds per 
square inch boiler pressure and the steam cut-off at %, or T 2 o 5 o 
of the stroke gave the best results, and represents a water con- 
sumption of about 26 pounds per horse power per hour ; that for 



A nd Its Appliances. 217 

60 pounds pressure, cut-off at T s & of the stroke a consumption of 
about 32^ pounds, and that for 30 pounds pressure, cut-off at 
T Vo" of the stroke ; corresponds to a consumption of 43 pounds 
of water per indicated horse power per hour. 

For a short distance on either side of these points of cut- 
off, the amount of water consumption is only slightly increased 
and the economy is practically the same, but in case of very 
early or very late cut-off the amount of water consumed is 
considerably increased ; the relation of economy to cut- 
off being well represented by these experiments in the 
diagram. 

In some similar experiments with a small (7x14) Buckeye 
automatic non-condensing engine, with a boiler pressure of 75 
pounds, the same experimenter has found the best rate of con- 
sumption to be 30 pounds of water at about j£ cut-off ; and 
while the most favorable point of cut-off is the same in small 
as in large engines, the matter of economical use of steam is 
in favor of the larger engine and high pressure. 

It should be understood that these results were deduced 
from refined tests, extending over a considerable period, the 
engines being in perfect condition as to leakage, etc., and the 
steam collected, condensed and carefully weighed after the 
work was performed, thus eliminating errors as far as possible. 

The steam was also practically free from moisture, as, in 
the tests of Fig. 106 it contained less than one per cent. 

From these and other similar tests we are enabled to form- 
ulate the following approximate rule for best cut-off. 

Divide 100 by 42 times the square root of the initial pres- 
sure and the quotient will represent the most favorable point 
of cut-off, expressed in fractions of the stroke. The initial 
pressure must be reckoned from a vacuum for condensing and 
from the atmosphere for non-condensing engines. 



2 1 8 Steam Engine Indicator 

In a test for ascertaining the economy of engines, it is very 
important that the quality of the steam used, or in other words 
the amount of moisture it contains, be determined. 

This quantity may be approximately found by making 
what is known as a calorimeter test, as explained in Chapter 
XXX. 

There are a number of instruments of variecj construction 
and principle, on the market for this purpose, with full and 
complete instructions for their use. 

In the absence of such a test, no accurate conception of 
the amount of steam actually used by the engine to produce a 
borse power per hour, can be obtained, for the steam may con- 
tain a large amount of ineffective moisture in the form of spray, 
which can only be detected either by an application of the 
calorimeter, or by collecting and weighing the exhaust. 

The generally acknowledged economy, that has been at- 
tained in the steam engine within the last thirty years, (esti- 
mate between thirty and forty per cent.) may be considered 
due, principally to the employment of multiple cylinder engines 
in connection with the best modern method of jacketing : also 
an increase of steam pressure, and superheating the steam ; 
either or all of which (when judiciously made use of) tends to 
better efficiency, and more economical results. 



.** 


**\ 


Mr 


* 


(</ 


\M 


vt< 


Mj 





And Its Appliances. 219 



CHAPTER XXVII 



BACK PRESSURE AND COMPRESSION. 



Back Pressure may be considered as one of the most serious 
losses in an engine, and represents the power expended in ex- 
pelling the exhaust steam, and in compressing steam into the 
clearance spaces, and is usually called the loss from back pres- 
sure, for it must be clearly understood that the direct steam 
does work in expelling the exhaust from the engine, as well as 
in driving the machinery to which the engine is connected. 

The whole of the back pressure cannot be removed, but a 
large proportion of the present losses would be avoided, if the 
clearance spaces were reduced to the smallest practical dimensions. 

The following diagrams Figs. 107 to 1 10 will serve to illus- 
trate the economy to be derived where small clearances prevail. 

The diagrams referred to, are theoretical, but in each case 
the assumed clearances (Fig. 107 being seven per cent, and Fig. 
109 being only two per cent.) are exactly with many of those 
found in different makes of slow speed engines. 

To obtain the maximum economical results with an engine 
at any given cut-off, compression should be carried up to, or 
very nearly the initial pressure of the cylinder. 

Where the clearances are large however, this is not always 
possible, especially with condensing engines, and without 
much consideration of the subject many builders of engines 
adjust the valve so that compression begins at about seven- 
eighths of the stroke. 



220 



Steam Engine Indicator 



In the diagrams the various compression lines are shown, 
and the results compared. The initial pressure is ioo pounds 
above zero in all, and the cut-off takes place at one-quarter 
stroke in each, so that when compression is carried up to 
initial pressure, the same quantity of steam, practically, is 
used per stroke in each engine irrespective of clearance, but 
the net power developed under those circumstances will differ 
very materially. 

The exhaust lines in the non-condensing diagrams are 0.3. 
pounds above atmosphere or 1 5 pounds above zero, and in the 
condensing diagrams 3.5 pounds above zero, or 11.2 pounds 
below atmosphere. 




Fig. 107. 
theoretical diagram with 7 per cent clearance. 

In Fig. 107 the solid lines represent diagrams from a non- 
condensing engine with compression A to initial pressure, and 
also compression B to 50 pounds, or one-half the initial pres- 
sure. 

The dotted lines represent the back pressure lines of dia- 
grams from a condensing engine, A 1, represents compression 
to initial pressure; B 1, compression to 50 pounds, and C, 
compression to 14 pounds. 



A nd Its Appliances. 221 

The initial pressure of theoretical diagram Fig. 107 is 100 
pounds above zero ; cut-off one-quarter stroke ; terminal pres- 
sure 30 pounds above zero, back pressure non-condensing, 15 
pounds and condensing 3.5 pounds above zero. 

From these diagrams the Available Power may be ascer- 
tained, which includes the amount absorbed in driving the 
engine as well as the effective power, and is usually designated 
the Indicator Horse Power, and written I. H. P. 

This is not the total power derived from the steam, but 
the I. H. P. must be known in order to ascertain the loss. 

The total power diagram of Fig. 107 is shown by the full 
lines in Fig. 108 and is determined as follows : During a single 
stroke of the engine piston, the indicator on that side where 
the steam is admitted will trace the upper line only of the dia- 
gram, the lower line being zero. 

The pressure of steam during that stroke being measured 
from the zero line (by the scale of the spring) consequently the 
total power exerted by the steam is proportional to the area 
enclosed between the zero line and the upper line of the dia- 
gram. 

If an indicator be placed in communication with the other 
side of the piston during the same stroke it will make the 
lower line only, or the back pressure line, (represented by the 
dotted lines in Fig. 108) of the indicator diagram. This line 
also in connection with the zero line forms another diagram, 
and the area enclosed between these lines, represents the power 
necessary to expel the exhaust steam during the first part of the 
stroke, and to compress steam into the clearance spaces during 
the latter part. 

The full lines of the diagram Fig. 108 show the total 
power exerted by the steam, and the dotted lines show back 
pressure from exhaust, and compression, or the resistance 



222 



Steam Engine Indicator 



which the direct steam must overcome before any useful work 
can be accomplished. 

The difference between the two is the power that must 
be expended before any is available for running the engine or 
driving the machinery and is a total loss. 





■ / 




I\ / 




1 » / 




.1 \ / 




1 ^ ^ 




1 N ^^ 




> ^A ^^^ 








\\ N v_-^^^ 






~-"V \ 






\J5 ^ 






\ ^ ^ ^ ^^ 












* ^ ^ *" ~ -^- ~ z^r^"^" 1 """"-- - ^r ^"-~-T"-~j"r i 






— — __ — ___ — ~ • — J=^!_-=_ as- _— — 





Fig. 108. 

It is evident at a glance of the diagram Fig. 108 that this 
loss is a large proportion of the total power and every means 
that will tend to reduce this loss should be adopted. 

As before mentioned the whole of this cannot be avoided, 
because it is impossible to obtain a perfect vacuum in an engine 
cylinder ; however the back pressure should be as low as pos- 
sible, bearing in mind that the clearance spaces should be filled 
with steam compressed (as near as possible) to the initial pres- 
sure at the end of the stroke. 

In the case of condensing engines having large clearances, 
this latter condition is difficult of attainment, and if strictly 
carried out would probably entail so much loss from increased 
back pressure as to off-set any gain from high compression. 

This points to the benefit of small clearances with which 
compression may be carried to any desired pressure. 

In Fig. 107 the mean effective pressure of the non-con- 
densing diagram compressed to initial pressure, (as line A), is 



A nd Its Appliances, 223. 

41 6 pounds, while the average pressure of the total power 
diagram Fig. 108 is 64 pounds, or about 54 per cento greater 
than the available power. 

In this case the only way of reducing the back pressure is 
to commence compression later in the stroke as shown by line B. 

The effect of this however, is a loss from low compression, 
as this is only carried to 50 pounds, and also from increased 
condensation. 

By comparing the results from the two diagrams it will be 
found that the latter has a mean effective pressure of 47 
pounds, making a gain in pressure of about 13 per cent over 
that of the former but there would be 14 per cent more steam 
necessary to fill clearance spaces, and the condensation would 
be increased more than 4 per cent., making a loss of 5 per 
cent, by not compressing to initial pressure. 

If this engine was condensing it would be practically im- 
possible to compress to initial pressure as in order to do so, it 
would be necessary to begin compression at the commencement, 
of the stroke with a pressure of 6. 5 pounds, above zero (line 
A 1), therefore 8.2 pounds would be the maximum vacuum that 
could be obtained in the cylinder ; consequently the highest 
pressure to which compression can be carried practically in this 
case is one-half the initial pressure or 50 pounds above zero 
(line B 1). 

The mean effective pressure of this diagram is 54.3 lbs. 
and the total power diagram as shown in Fig. 108 is 64 pounds 
or about 18 per cent, greater; however there would be 14 per 
cent, more steam required than when compressing to initial 
pressure, and condensation would be increased fully 4 per cent. 

If compression did not commence until later in the stroke 
and only carried up to 14 pounds (line C), the mean effective 
pressure would be 59.6 pounds or 9.8 per cent, more than the 
previous diagram, but over 24 per cent, more steam would be 
required than if compression were carried to initial pressure,. 



224 



Steam Engine Indicator 



and the extra condensation would amount to 6.9 per cent, or a 
loss of 3 per cent, over the previous diagram with greater com- 
pression. 

Comparing the later diagram (line C), with the total power 
it will be seen that the total power is but 7.5 per cent, greater, 
and it is this near approach to the total diagram, that makes 
the condensing engine so much more economical than the non- 
condensing, and a moderately well loaded engine gives better 
results than one lightly loaded, as in the case of a lightly 
loaded engine, the waste power remains the same, and conse- 
quently the percentage of loss increases ; although both the 
total, and available power are less. 

In the first diagram the steam developed over 3 horse- 
power to make 2 horse power available, or a loss of 35 per cent. 
In some very lightly loaded engines, the steam develops over 3 
horse power to make 1 horse power available, or a loss of 70 
per cent. 




Fig. 109. 
theoketical diagram with 2 per cent clearance. 

Initial pressure ioo pounds above zero: cut-off, one-quar- 
ter stroke ; terminal pressure 30 pounds above zero ; back 
pressure non-condensing 15 pounds and condensing 3.5 pounds 
above zero. In Fig. 109 as in Fig. 107 the full lines represent 



And Its Appliances. 225 

diagrams from a non-condensing engine with compression A 
to initial pressure, and compression B to 50 pounds above 
zero. 

The dotted lines represent the back pressure lines of con- 
densing diagrams, with compression A 1, to initial pressure, 
also compression B 1, to 50 pounds pressure and compression 
C to 14 pounds above zero ; therefore the two diagrams Figs. 
107 and 109 are identical in all respects except in their amount 
of clearance. 

The total power diagram of Fig. 109 is shown in full lines 
in Fig. 1 10, and the back pressures and the compression curves 
are shown by the dotted lines ^, A 1, B, B i, and C. 

The mean effective pressure being determined in the same 
manner as in the previous diagrams. 

In Fig. 109 the mean effective pressure of the non-con- 
densing diagram compressing to initial pressure (line A) is 44 
pounds and the average pressure of the total power diagram 
Fig. 1 10 is 60.8 pounds or about 38.5 per cent greater than the 
available power. 

This is quite a loss, but it is a decided improvement over 
the percentage of loss shown by the diagram with large clear- 
ance, as in Fig. 107. 

If in this case the compression had been carried to 50 
pounds only, (line B), the mean effective pressure would have 
been 45.6 pounds or 3.6 per cent, greater pressure, but there 
would be over 4 per cent, more steam required to fill the clear- 
ance spaces, and the condensation would be increased over 3 
per cent., making a loss of about 3.5 per cent, by the lower 
compression. 

With the condensing diagram Fig. 109 it will be seen that 
compression may be carried to initial pressure, (line A) and the 
mean effective pressure in this case would be 52.8 pounds. 

If the compression had been carried to 50 pounds only, 
(line B), the mean effective pressure would have been 56 



226 



Steam E?igine Indicator 



pounds, or an increase of 6 per cent, in the pressure ; but as an 
off-set, over 4 per cent, more steam would be required to fill the 
clearance space, and the condensation would be increased more 
than 3 per cent., leaving a loss of 1 per cent. 

If the compression had been still lower, (line C), the mean 
effective pressure would have been 57.5 pounds, or an increase 
of 8 per cent, in the pressure; but there would be 7 per cent, 
more steam required to fill the clearances, and condensation 
would be increased over 5 per cent., making a loss of 4 per 
cent, by the low compression. 

Comparing the results obtained from the two diagrams, 
the saving effected by an engine having small clearance will 
readily be seen, and as this has such an important bearing on 
the economy of the engine, small clearances should be strictly 
insisted upon. 

There are many slow speed engines in use at present hav- 
ing less than 3 per cent, clearance, and this amount should 
therefore be the maximum allowed in slow speed engines, 
either simple or compound. 




Fig. 110. 



Full lines show theoretical diagram of total pressure 
exerted by the steam. 



A nd Its Appliance. 



227 



Dotted lines show back pressure from exhaust and com- 
pression, or the resistance which the direct steam must over- 
come, before any useful work can be accomplished. 

COMPARISON OF RESULTS. 



Non-Condensing 'Diagrams. 

Clearance 7^ 2% 

Cut-Off 25^ 2S% 

Terminal Pressure 3olbs. above zero 26-5IDS. above zero. 

Back ,l i5lbs. '« " islbs. " " 

M. E. P. M. E. P. 

Compression to Initial pressure and Gain compared with 

using equal quantities of steam larger clearance, 

per stroke in both engines ... 41 -61bs. . . . 4/j.lbs. 5 S% 

Loss by Compressing to solbs 
pressure in place of full Com- 
pression 1% 3-5$ . 7-3$ 

Condensing Diagrams. 

Clearance 7% 2% 

Cut-Off 25^ 25% 

Terminal Pressure 3olbs. above zero 26 ^lbs. above zero. 

Back " 3"5lbs. " " 3*5lbs. 

Gain compared with 
larger clearance. 

Compression to Initial pressure . — — 8^ 

Loss by Compressing to solbs. 
pressure in place of full Com- 
pression 6% 1% 13% 

Loss by Compression to i4lbs. 
pressure in place of full Com- 
pression 9% 4.% 13% 

In Compound Engines the greater economy will be obtained 
when expansion is carried down to the back pressure in each 
cylinder, except the last, and Compression is carried up to In- 
itial pressure in all ; with no drop or free expansion between 
the cylinders. 



22$ Steam Engine Indicator 



CHAPTER XXVIII. 



COMBINING DIAGRAMS FROM COMPOUND ENGINES 



Compound engines, for almost all purposes are now com- 
ing into more general use each year ; but in the use of the in- 
dicator upon them, both cylinders are treated as simple engines, 
the power of each being added together. 

The diagrams from both cylinders can be taken with the 
same denomination of spring if desired, but usually a compar- 
atively light spring is used on the low pressure in order that 
the dimensions or area of the diagram may be increased. 

The compound engine with receiver, is as two engines, 
one high pressure non-condensing, and the other a low pres- 
sure condensing engine, but from the fact that the same steam 
is used in both cylinders, the action of the steam must be con- 
sidered as if used in a single engine, and the diagrams from 
each cylinder must be combined, to form an equivalent simple 
one. 

Before making combinations of diagrams from the high 
and low pressure cylinders of compound engines, the object of 
combining them should be first understood. 

There are certain losses in single or non-compound en- 
gines which are corrected to a great extent by compounding, 
but this in turn introduces other losses which it is desirable to 
reduce to the least possible amount. 



And Its Appliances. 229 

These losses are between the two cylinders, and consist 
of, condensation in the passages, pipes, and receiver (if one be 
used), friction in the steam ports and pipes, and expansion of 
the steam that takes place between the two cylinders without 
doing useful work. 

The extent of these losses can be shown by combining the 
diagrams from the two cylinders and drawing in the hyper- 
bolic curve. This curve should just touch the expansion line 
of the high pressure diagram at a point where the exhaust 
from the cylinder begins, and the space between the curve and 
both diagrams below this point, and also the space between the 
two diagrams, represent the loss between the two cylinders. 

To correctly combine the two diagrams, the clearance in 
each cylinder should be known and accounted for, as well as 
the piston displacement, and the relative length of the two 
diagrams when combined, is as the ratio of the total volume of 
the cylinders, that is; the piston displacement plus the clear- 
ance at one end. 

To do this, a base line may be taken if desired and divided 
into two parts, which have the same relation to each other in 
length, as the total volume of the cylinders. The short por- 
tion of the line will represent the small or high pressure cylin- 
der, and on this length the diagram from this cylinder is con- 
structed from the lowest pressure, and on the longer portion of 
the line the diagram from the large cylinder is laid out. 

It is best however to decide on the total length of the low 
pressure diagram first, and a length that can be easily divided 
into 100 parts will be found most convenient, as percentages of 
this length can then be easily measured; for example, 10 inches 
for a scale of tenths, or 12^ inches for a scale of eighths. The 
combination diagram, Fig. 113, was drawn 12^ inches long, 
and photo reduced to the length shown. 

It now becomes necessary to decide on the scale of the 
spring to which the two diagrams are to be plotted ; usually it 



230 



Steam Engine Indicator 



will be found most convenient for this to take the scale of the 
low pressure diagram ; then draw in the atmospheric, and va- 

n 



Pig. 111. 





« 1 








1 


i l— 

1 

1 | 

i 

i 

i i 
i i 




1 
J 
1 

1 /I 
1 /l 

1/ i 




ft 


1 


1 

7| 


*l 


ft 


i 1 

i 


1 

A] 


/ i i 

i 


1 h° 


i i 

41 ?l 




Fig. 112. 
cuum lines, and erect perpendiculars at the two extremes of 
the combination diagram, one of which is the clearance line. 

All measurements of distance should be made from the 
clearance line, and all measurements of pressure from the 



And Its Appliances. 



231 



atmospheric line. Now divide each original diagram into any- 
desired number of equal parts, 10 being a good number. 

Find the volume of the piston displacement of the low 
pressure cylinder, to which add the volume of the clearance ; 
the total length of the diagram represents this total volume. 

Divide the clearance by the total volume, and the quotient 
will be the percentage this clearance bears to the whole length. 




Fig. 113. 

Set off this distance from the clearance line, and divide 
the remainder (representing the piston displacement) into the 
same number of parts that the original diagram is divided into. 

If the scale selected is the same as that of the original dia- 
gram, simply transfer the pressures directly with a pair of di- 
viders from the lines on the original diagram to the corres- 
ponding lines on the combination ; then draw in the connecting 



232 Steam Engine Indicator 

portions of the diagram, and the result will be an elongated 
diagram from the low pressure cylinder or as if it had been 
taken with the same spring as before, but with a proportion- 
ately enlarged paper drum. 

Now find the total volume of the high pressure cylinder, 
and divide it by the total volume of the low pressure cylinder, 
and the quotient is the percentage of length of the diagram, 
which should be measured from the clearance line. 

Divide the clearance volume of the high pressure cylinder 
by the total volume of the low pressure cylinder and measure 
off the percentage of length, as before, from the line. 

Divide the remaining length of the high pressure diagram 
(representing the piston displacement) into the same number 
of parts as the original diagram, and transfer the pressures 
from the lines on the original diagram to the corresponding 
lines on the combination and to the new scale of pressures. 

If the original high pressure diagram was taken with a 40 
spring, and the combination diagram made to a scale of 10 lbs. 
per inch, then the new diagram will be four times as high as 
before, although it may be shorter. 

Next draw in the hyperbolic curve ; (a method of doing 
this is given on page 10 1, Fig. 56) and the two diagrams thus 
combined will form a single one. 

The process of combining indicator diagrams from com- 
pound engines is both interesting, and instructive to the en- 
gineer in various ways, and usually attended with most satis- 
factory results. 

Diagram Fig. 113 is a combination of the diagrams Figs. 
1 1 1 and 112, and were taken from a tandem compound engine. 

In order to make the foregoing explanation more clearly 
understood, diagrams Figs, in, 112 and 113 have the con- 
struction lines shown, and the necessary calculations are given 
below. Fig. 113 was drawn 12^ inches long over all and re- 
duced by photo engraving process to its present length. 



A nd Its Appliances . 233 

Diameter of H. P. Cylinder - - 30 in. 

" L. P. - - 50 in. 

Stroke of Pistons - - - 72 in. 

Diam. of Piston-rod, both Cylinders 6}( in. 

Volume of High Pressure Cylinder — 

(706-86— 30-68)x 72 = 48685 cubic inches. 

Clearance volume = 2545 " " 

Total volume 51230 
Volume of Low Pressure Cylinder — 

(1963*50— 30-68)X 72= 139163 cubic inches. 
Clearance volume = 7673 " " 

Total volume 146836 
Total length of L.P. card, I2j£ inches, or 100 eights; scale 

7^7 3 X 100 

10. Length of L.P. clearance, marked A on diagram, — - ° 

146836 

= 5*22# of total length or -f-f-Aim The remainder of the 
length, representing the piston displacement, is divided into 
10 parts, the same as original diagram, and the pressures trans- 
ferred to the corresponding lines. 

Total length of H.P. card, or B+C on diagram, 5 I23 ° X IO ° 

1 246836 

= 34-89^, or 4f| in. Length of H.P. clearance, marked B on 

diagram, — -^- — -— =1*73^, or A in., leaving the distance 
146836 

marked C, representing the piston displacement, which is di- 
vided to correspond with the original diagram, and the pres- 
sures transferred either with scales or dividers ; in the latter 
case each distance must be multiplied four times. Draw in 
the connecting portions of the diagrams, taking care to follow 
the contour of the original as closely as possible ; and finally 
the hyperbolic curve is drawn in, 



234 Steam Engine Indicator 



CHAPTER XXIX. 



DIAGRAMS FROM GAS AND OIL ENGINES AND AMMONIA 
COMPRESSORS. 



In the last few years the large increase in the number of 
gas and oil engines in nse for all kinds of manufacturing enter- 
prises both at home and abroad, has been most remarkable, and 
their number and power are still increasing each year, so that 
now these motors are in competition with steam engines in 
almost all progressive countries. 

The fact that both gas and oil engines now run with 
greater regularity than in the past is principally due to im- 
proved and better governing arrangements. The portability 
of small oil engines renders them very convenient for use in 
country towns, and other places where gas is not made. A 
greater part of these motors work with the four-cycle, and with 
lift valves. 

Gas engines are in most cases single acting and single cyl- 
inder, except for the largest powers, when two cylinders are 
generally used. 

The charge is usually fired either by tube ignition, or b\ 
an electric current. The piston speed usually varies from 500 
to 700 feet per minute, and the clearance volumes of the cylin- 
der are much larger than in steam engines, usually from 20 to 
50 per cent, of the piston displacement, against from 3 to 8 
per cent, in steam engines. 



And Its Appliances. 



235 



When considering- that in the employment of gas engines 
no fuel is being consumed when the engine is not in actual 
operation, it is evident that they form economical motors when 
small powers are required, and will soon come into more ex- 
tensive use as affording a cheap, and efficient motive power in 
a great number of places where the use of steam is difficult or 
impossible. 

Owing to the greatly increased initial pressure in the cyl- 
inders of these engines, (being principally due to the explosive 
mixture employed therein) specially designed indicators have 
been constructed to better meet the requirements necessary, 
and provide means for indicating pressures ranging frdm 300 
to 600 or more pounds pressure per square inch. 

This is accomplished by making provision in the construc- 
tion of the instrument, whereby a piston can be used of a small- 
er size than the piston of one-half square inch in area, as ord- 
inarily used in most makes of indicators. This smaller piston is 

usually made one-quarter of a sq.inch 
in area, or one-half that of the former, 
and which when in use, results in 
doubling the readings or amount of 
pressure, as when used with the 
same denomination of spring in con- 
nection with the larger piston. Fig. 
1 14 represents the manner of con- 
struction in combining the half and 
quarter inch area piston in one in- 
strument, as applied to the Tabor 
Indicator, whereby the use of the 
C~ f;}JLX[! BHIll one-half inch piston for low pres- 

sures, or in which the quarter inch 
piston may be used for the very high 
FlG - 1U - pressures often attained in some oil 

and gas engines. Either of these pistons may be used 




236 Steam Engine Indicator 

independently as desired, without any change whatever either 
in the spring or any part of the instrument. 

In the illustration the half inch piston is not shown ; but 
instead the quarter inch piston is represented attached to the 
spring in position for operation. 

The body A. of the instrument is shown partly in section 
in order that the location of the parts may be readily observed. 
B. is the piston cylinder in which the half inch piston works, 
and which is sreewed at its lower end into the body A. C. is 
the piston cylinder in which the quarter inch piston works, 
and is formed in the upper end of the tube G. 

D. is the quarter inch piston, and is sufficiently elongated 
as to reach and work in the cylinder C. Its up*per end is 
threaded and screws into the mounting of the indicator spring. 
It is made in the form of a shell, and the pencil mechanism is 
secured to it by means of the extended thumb-nut E. F. is 
the usual connection for securing the indicator to the cock. 
H., I. and J. are respectively the cylinder cap, swivel plate 
and piston rod. 

In addition to obtaining the most accurate results from 
high pressures by the use of the smaller size of piston, this 
combined indicator has another advantage in that it requires a 
less number of springs for any given range of pressure. 

For example : A 50 spring may be used in connection with 
the larger piston to 120 pounds pressure per square inch, but 
by substituting the smaller piston, pressures may be indicated to 
240 pounds with the same denomination of spring; a range 
that would otherwise require two springs ; thereby doubling 
the range of the instrument with a single spring. Figs. 1 15 to 
1 1 8 inclusive represent diagrams taken from the Springfield Gas 
and Gasolene engines. Fig. 115 is from a 7^ inch diameter 
of cylinder by 14 inches stroke, running 200 revolutions per 
minute, with scale of spring 120. 



And Its Appliances. 



237 



Fig. 116 is from a 13 inch diameter of cylinder by 24 
inches stroke, running 160 revolutions per minute, with the 
scale of spring 120. 




Fig. 115. 
Each of the above may be considered as ideal cards in 
every respect. Figs. 117 and 118 are from gasolene engines 




Fig. 116. 
presented simply for the purpose of showing some bad cards. 
Fig. 117, shows the effect of late ignition, while Fig. 118, 



238 



Steam Engine Indicator 



shows also late ignition, and a stratified condition of the 
charge. This is indicated by the waving expansion line, each 
waving being an independent explosion or combustion. 




Fig. 117. 

These two latter cards were taken expressly for the pur- 
pose of showing these very things. Fig. 1 19 represents a pair 
of superimposed indicator diagrams taken from a 20 by 26 inch 
steam cylinder, driving a double-acting ammonia compressor 
from a Buffalo Refrigerating plant, making 26 revolutions per 
minute, and are ideal diagrams in almost every respect. How- 
ever where the speed of the engine is slow, as in refrigerating 
machines they are only what might be expected, as the exist- 




Fig. 118. 
ing conditions are generally favorable for the production of 
good diagrams ; because a longer interval of time is given to 
the steam to pass through the steam ports and fill the cylinder 



And Its Appliances. 



239 



nearly to boiler pressure at the commencement of the stroke, 
and thus continue to the point of cut-off; and where the steam 
admission is regulated hx an automatic system of valve gears 
(such as in this case) we find the cut-off well defined, the ex- 



SCAXE, 40 U>s. PiB Sli. ..M-tt. 




Bteain Cylinder... A. 20 *29 



Fig. 119. 
pansion line all that could be desired, and the back pressure 
line nearly straight. 

Figs. 120 and 121 represents diagrams taken from the gas 
or ammonia cylinder which is 15 inches in diameter by 26 inch. 

Scats, 80 lbs. rEB Bq. Ihoh. 




Discharge Pressure _ 120 lbs. 

Suction Pressure _ 25 lbs. 

Devolutions permln... „ „36. 

Indicated Horse Power of Gas Cylinder, 344 



Fig. 120. 
stroke. The diagrams from each show that 40 horse power 
was developed by the steam engine, while 35.4 horse power 
were needed to compress and discharge the gas within the 



240 



Steam Engine Indicator 



compressor. The difference between the two, namely 4.6 horse 
power, represents the loss caused by friction, amounting to 





Scale, 80 lbs. pee. Sq. Ikch. 




r~ 


\ N." N >, 




"" 


"n. \_ x x^ 




\ 




^^^iij-^ 


Gas OyUod«_._15*X86" 





Fig. 121. 




Fig. 122. 
1 1.5 per cent, of the steam engine work, or 13 per cent, of the 
work accomplished with the gas cylinder. 




Fig. 123. 
The mean effective pressure of the compressor diagrams 
Figs. 120 and 121 are computed in the same manner as that for 



And Its Appliances. 



241 



the steam cylinder and the power developed is determined by 
the same rule. As the difference is but 4.6 horse power, it 
demonstrates that 88.5 per cent, of it is made to do useful 
work. 




Fig. 124. 

Figs. 122 to 125 represent diagrams from an Otto gas 
engine with a diameter of cylinder of 6^ inches, and the length 
of stroke \^/> inches. The number of explosions per minute 
being 130, and the number of revolutions per minute 260. 
Scale of the spring 208. 




Fig. 125. 

The following original diagrams Figs. 126, 127 and 128 
were taken from a rated 7 actual horse power Priestman safety 
oil engine. Diameter of cylinder 8 inches by 8 inches stroke 
making 350 revolutions per minute, the scale of the spring 



242 



Steam Engine Indicator 



being- ioo. These three cards comprise a set, being full load, 
half load, and friction load with the above data. 




Fig. 126. 




Fig. 127. 



Fig. 128. 

A computation of the diagram at full load Fig. 126 shows 
the engine to be developing 9.41 indicated horse power. 

There are still many places where power cannot be ob- 
tained, except through some form of heat engine, and where 
steam is unsuitable, and gas perhaps not available, the oil en- 
gine has frequently presented itself and proved quite satisfact- 
ory in all such cases. 

It is customary to consider oil and gas engines as being 
practically alike; but there is one notable difference, in that, 
if an oil engine is run without load it is very liable to stop. 
This applies only to that type which has no external ignition 
to itself, neither by electricity nor otherwise, but ignites only 
by means of a heated chamber which is kept to ignition tem- 
perature by the repeated explosions of the charges. 



And Its Appliances. 243 

In this class of oil engine the oil is injected by a small 
pump into what is called the vaporizer ; the Otto cycle is 
worked and ignition takes place when the mixed change of air 
and vapor becomes compressed in the hot vaporizer, the tem- 
perature of which is kept up to redness. 

In starting these engines the vaporizer is first heated by a 
lamp blown by a fan, or by a retort blown by its own self -gen- 
erated oil gas. After being once heated the vaporizer is kept 
hot by the recurring explosions. With a light load there are 
necessarily many explosive strokes cut out by the governor, 
the same as in case of the gas engine. This so reduces the 
generation of heat in the cylinder, that the vaporizer is not 
maintained hot enough to ignite the vaporized oil and the 
motive power is not produced, and consequently the -engine 
stops. From this it is clear that the size of an oil engine must 
correspond fairly close with the load to be driven, or else the 
number of idle strokes will be such, as to prevent the main- 
tainance of a sufficient temperature in the vaporizer to ignite 
the charge. 






244 Steam Engine Indicator 



CHAPTER XXX. 



MAKING CALORIMETER TESTS. 



When testing engines to determine their economy, careful 
tests should be made of the quality of the steam entering the 
engine, as in many cases -water is carried over from the boilers, 
and condensation in the steam pipes also adds to the amount. 

The priming of boilers is a serious loss in many steam 
plants, and for the lack of proper appliances for determining 
the same, it goes on unchecked, and often unknown. 

A large proportion of the loss from the priming of boilers 
can be prevented if proper precautions be adopted, and thereby 
a saving of coal effected. 

Long steam pipes also invariably cause condensation, and 
it is very essential that none of this water should pass into trie 
engine, as it occasions a serious loss by promoting initial con- 
densation in the cylinder ; therefore, an efficient water separator 
should be placed in the steam pipe near the engine in order to 
remove the water of condensation (as near as possible,) from 
the steam, 

The Calorimeters that are being used at the present time, 
are of three kinds, namely : The condensing or barrel calor- 
imeter, the throttling or superheating, and the wire-drawing. 

In the first of these, a certain weight of cold water is 
utilized to condense a certain weight of steam, and its temper- 
ature is raised by the heat in the steam to a certain higher 



And Its Appliances. 245 

temperature, depending upon the amount of moisture in the 
sample of steam condensed. With a device of this kind, (a 
primitive form,) the appliances for determining the weight, 
and the temperature must be very sensitive, and the readings 
carefully observed in order that the results may be approxi- 
mately accurate. 

In the second mentioned, (the throttling calorimeter,) the 
quantity of heat is ascertained, that is requisite to evaporate, 
and also slightly superheat the moisture contained in the sam- 
ply of steam tested, and depends upon the fact, that steam 
which contains a moderate amount of moisture will become 
superheated if the pressure is reduced by throttling, without 
loss of heat. 

This instrument is not only easier to use, when the amount 
of moisture is not excessive, but the quantities are more ac- 
curately measured than in some other forms of calorimeters. 

It is, however, somewhat limited in its range, and the calcu- 
lations rather complicated for other than an expert. 

The third form of instrument, or wire-drawing calorimeter, 
operates also by superheating, but neither does this instrument 
depend on any exterior source of heat for this purpose, because 
(as in the former case,) steam containing a small amount of 
moisture when wire-drawn, becomes superheated at the lower 
pressure ; the amount of the superheat depending directly on 
the percentage of moisture in the steam previous to wire- 
drawing. 

In this instrument the percentage of moisture may be very 
accurately determined, but like the throttling calorimeter, its 
range is also somewhat limited, and the calculations compli- 
cated for the ordinary engineer. 

There is still another form of the instrument, which con- 
sists of a wire-drawing device and separator combined. 

The steam first enters the water separator, in which nearly 
all of the moisture is separated from the steam before it passes 
to the wire-drawing device. 



246 Steam Engine Indicator 

The water which has been separated from the steam may 
be drawn off, and weighed separately, and the remainder of 
the moisture is determined by the amount of superheat in the 
steam after being wire-drawn. 

In all of the above mentioned calorimeters, the steam sup- 
ply is taken from the main steam pipe, by means of a small 
pipe which extends nearly across the main pipe, and is perfor- 
ated its entire length in order to obtain as nearly as possible, 
an average sample of the steam passing through the pipe. 

The rules, formulas, and directions for the use of some of 
the modern forms of calorimeters are commendable for their 
accuracy and in some cases simplicity, but the principles upon 
which their operations are based, and results obtained, are in 
many cases beyond the comprehension or understanding of the 
ordinary engineer unless he is proficient in the higher branches 
of mathematics. 

Probably no single operation pertaining to the science of 
steam engineering requires greater care, manipulation, and 
accuracy in making steam tests than in the use of the calori- 
meter. Therefore, it will be the endeavor here to present this 
important subject in as simple a manner as possible in order 
that engineers not sufficiently versed in the higher mathematics 
may obtain the benefit of the science connected therewith. 

In testing a steam boiler for evaporation alone, without 
the calorimeter test, but little information is gained so far as 
the efficiency of the boiler is concerned ; because to determine 
the real efficiency and economy in a steam boiler, the quality of 
the steam generated must be ascertained ; as well as the quan- 
tity of water evaporated per pound of coal, or per pound of 
combustible. 

The principle cause of priming in boilers is due to 
a faulty construction, and without the calorimeter test the 
faulty constructed boiler may, if judged from the amount of 
water evaporated, show greater efficiency than the properly 



And Its Appliances. 247 

constructed boiler. If a boiler on being tested carried off a con- 
siderable amount of water with the steam, it would be unfair 
to credit it with the evaporation of such water into steam, 
because it has only supplied enough heat to the water carried 
over to the engine as to raise it from the temperature of the 
feed water to the boiling point : this quantity of heat being 
only a fraction of that required for its evaporation : Therefore, 
every pound of surplus water carried off with the steam takes 
a correspondingly amount of heat from the boiler, according to 
the quantity of surplus steam carried over, and without produc- 
ing an equivalent in work performed. The result of priming 
is also greatly detrimental to the performance of the engine 
supplied with steam from such a boiler. It, therefore, becomes 
necessary with work in which there is to be any degree of 
accuracy, to determine the quality of the steam used, that is : 
what percentage of it is actually steam, and how much of it is 
water. 

The main object is to obtain steam as dry as possible, 
without superheating it ; and the boiler that will furnish such 
steam, and perform the greatest amount in proportion to the 
amount of fuel consumed, may usually be considered the best 
boiler, all other things being equal ; such as proper setting of 
boilers, and properly constructed furnaces, etc. 

Of the devices here mentioned, the most available, simple, 
and comprehensive for the working engineer, is the condens- 
ing or barrel calorimeter of the primitive form, with which 
almost any one interested in the subject may equip himself at 
little expense, and gain a great amount of information not 
easily attainable by any other means. 

It consists of a simple barrel placed upon a platform scale 
as shown in Fig. 129. In the figure A. represents the main 
steam pipe, and shows how the attachment is made, and B. 
represents a standard (made suitable for the purpose,) to which 
the calorimeter pipe is secured. 



248 



Steam Engine Indicator 



That part of the pipe that is inside the main steam pipe 
should be of one-half inch gas pipe, closed at the end, and per- 
forated, as shown, with small holes about one-eighth inch in 
diameter. 

To the valve attached to the opposite end of this pipe it is 
1 good plan to have a petcock screwed into the top for the pur- 
pose of being opened after a test has been completed, to allow 
any water that may remain in the pipe between the valve and 
the barrel, to fall to the level of the water in the barrel. 
The down pipe leading from the valve should have a small 
rubber hose attached to the end of the pipe, as shown in the 
figure, and reach to within a short distance of the bottom of 
the barrel. 




Fig. 129. 

The lower end of the hose should be closed, and the hose 
above that perforated laterally all around with small holes, to 
avoid the jar due to condensation. 

The barrel employed for this purpose should be in such 
condition as to absorb as little water as possible while making 
the test. 

In platform scales where the beam is graduated to one- 
half pounds only, it is possible, if so desired, to read to 
one-tenth or even one-twentieth of a pound, by employing in 



And Its Appliances 249 

connection with the first weight an additional movable weight 
one-tenth of the weight of that of the first. 

There should be suspended in the barrel, (in any con- 
venient manner as will be easily accessible for handling and 
observation,) an accurately graduated thermometer, capable of 
being read to at least one-quarter of a degree. 

The empty barrel should be accurately weighed and its 
weight carefully noted ; after which (for convenient calculation) 
put an even number of pounds of water into the barrel, leaving 
sufficient room in the top for the desired amount of condensed 
steam. 

Then set the scales so that they will balance after five or 
six per cent, more water has been added in the form of con- 
densed steam. Now remove the hose from the barrel, open 
the valve and let the steam blow through long enough to heat 
the pipes thoroughly. 

During the time the steam is blowing through, take the 
temperature of the water in the barrel, and carefully make 
memoranda of the same. 

Shut the steam off, insert the hose into the barrel, and again 
turn the steam on, and as the temperature increases, gently 
stir the contents with a light wooden stick, in order to insure 
the mixture being of a uniform temperature at the time the 
thermometer is read. 

It is not advisable to supply steam any longer than to 
raise the temperature of the water in the barrel to about 110 
degrees, as beyond this temperature, radiation may take place 
to such an extent as will complicate the tests, and also the re- 
sults. 

It is desirable to have the water as cold as possible to 
begin with, as the greater the amount of steam condensed, the 
less will be a given error in determining its weight and pro- 
portion. 



250 Steam Engine Indicator 

In a short time after the steam is turned on. ascertain how 
near the scale is in balance again, by placing the hand under 
the scale beam and raising it gently, and as soon as it is found 
that the scales are about to balance, shut the steam off, open 
the petcock and then balance the scales. 

Then take hold of the thermometer and stir it around 
gently in the water and carefully observe the highest tempera- 
ture reached. 

Make memoranda of the same, and also note the weight of 
water in the barrel. 

The pipe leading from the main steam should be carefully 
felted and thoroughly heated previous to each experiment, by 
wasting steam through it before placing the hose into the cal- 
orimeter. Suppose that 360 pounds to be the original weight 
of water put into the barrel at the beginning of the test ; the 
water being at a temperature of 50 degrees Fahrinheit. 

Now suppose steam of 100 pounds guage pressure, (equiv- 
alent to 115 pounds absolute pressure) be run into the water 
until the temperature is increased to no degrees Fah., and 
that upon re weighing its weight has been increased by 20 
pounds ; this being the amount of steam condensed in raising 
its temperature. 

Referring to the table No. 9, on the properties of water 
at each degree of temperature it will be found that one pound 
of water at a temperature of 50 degrees Fahrenheit, con- 
tains 50.003 heat units; and water at a temperature of no 
degrees Fah. contains 1 10. 1 10 heat units per pound. 

By reference to the table No. 8, on the properties of sat- 
uarated steam at different pressures, it will be found that steam 
at 100 pounds gauge pressure, (corresponding to 115 pounds 
absolute,) contains 1216.97 heat units per pound of steam. 

Then we have : 

360 pounds^ weight of water in the barrel before adding 
steam. 



And Its Appliances. 2 5 1 

50.003 = number of heat units per pound of water at 50 
Fahrenheit before adding steam. 

1 10. 1 10= number of heat units per pound of water at 1 io° 
Fahrenheit, the temperature after adding steam. 

20 pounds = weight of condensed steam and water added 
to the water in the barrel. 

380 pounds = weight of water in the barrel after adding 
condensed steam and water. 

12 16.9741 = number of heat units in one pound of dry 
steam at 100.304 pounds gauge pressure. 

The percentage of water in the steam may then be calculated 
by the following Rule : 

First : Subtract the number of pounds of water contained 
in the barrel before the condensed steam was added from the 
total number of pounds in the barrel after the condensed steam 
was added, and multiply the remainder by the total heat units, 
as shown by the table, contained in one pound of steam due 
the pressure per square inch indicated by the steam gauge dur- 
ing the time the test was made, and the product will give the 
total heat units that would have been contained in the steam 
that has been discharged in the barrel if the steam had been 
dry. 

Second : Multiply the number of heat units contained in 
one pound of the heated water in the barrel by the number of 
pounds of such water, and the product will give the total 
number of heat units contained in the heated water in the 
barrel. 

Third : Multiply the number of heat units contained in one 
pound of unheated water in the barrel by the number of 
pounds of that water, and the product will give the total num- 
ber of heat units in the unheated water in the barrel. 

Fourth: Subtract the total heat units in the unheated 
water in the barrel from the total heat units contained in the 
water after being heated, and the remainder will give the 



252 Steam Engine Indicator 

number of heat units that have been added by the steam and 
water discharged into the barrel from the steam pipe c 

Fifth : Subtract the heat units that have been added to the 
original water in the barrel, from the total heat units that 
would have been contained in the steam if the steam had been 
dry, and the remainder will show the difference in heat units 
between dry steam and the steam discharged in the barrel. 

Sixth: Multiply the heat units as shown in table No, 8, 
contained in one pound of steam due the pressure per square 
inch as shown by the gauge during the test by the number of 
pounds of steam and water that have been added to the orig- 
inal water in the barrel and the product will give the total 
number of heat units that would have been contained in the 
steam that has been discharged in the barrel if the steam had 
been dry. 

Seventh: Divide the difference in heat units between dry 
steam, and the steam discharged in the barrel, by the total 
heat units contained in the dry steam, and multiply the quo- 
tient by 100, and the product will give the per cent, of water 
contained in the steam discharged into the barrel. 

This rule may be resolved into a formula from the data 
given as follows : 

Let H. = total heat of steam at observed pressure = 12 16.97 
heat units per pound. 

Let h 1. = weight of water added by heating with steams 
20 pounds. 

Let W. = weight of water in the barrel before adding 
steam = 360 pounds. 

Let w 1. = weight of water in the barrel after adding 
steam=38o pounds. 

Let t. = total heat of water per pound corresponding to in- 
itial temperature of water in the barrel at 50 Fah.=: 50,003 
heat units. 



A nd Its Appliances. 253 

Let T. = total heat of water per pound corresponding to 
final temperature of water in the barrel at 1 io° Fah.= 1 10. 1 10 
heat units. 

Let E. — heating efficiency of the steam furnished com- 
pared with the saturated steam between the same limits of 
temperature. 

Let Q. = quality of steam furnished. 

Then Q. = Hxh 1 — (Txw 1 — tx w)x 100=2. 04+per cent. 

Hxh 1 

Or, by figures as per data, 

Q= (12 16.97 X 380— 360) — ( 1 10. 1 10 X 380— 50.003 X 360) X 100= 

1216.97X 20 

2. 04+per cent of water in the steam discharged in the barrel. 

The value of E may be ascertained by the following formula : 

W (T— t) 
E=- — J=- — y =.9774 heating efficiency of the steam, or by 

- „ 360 (1 10. 1 10— 50.003) ,, « 

fiorures E = - — = .97 74= same result as above 

20(1216.97—110.110) 

in heating efficiency. 

If the steam is superheated it will show a greater number 
of heat units per pound for a given pressure than is contained 
in the standard steam as shown in table No. 8. 

The total heat of steam at any given pressure corresponds 
to a pressure of 14.7 pounds above the given pressure, or that, 
as shown by the steam gauge. 

This plan of making such a test is given as being the most 
available and most simple of comprehension to the ordinary 
working engineer. At the same time the greatest care and 
vigilance must be observed throughout in order to get fairly 
accurate results, as an error of one-quarter of a pound in de- 
termining the amount of steam condensed, will make a differ- 
ence in the result of about three per cent. Also an error of 
one-half a degree in temperature will make a difference in the 
result of at least one and one-quarter per cent. 



254 Steam Engine Indicator 

The scales must be carefully standardized, and as sensitive 
as possible and greater accuracy may be attained by secur- 
ing- a pointer to the scale beam, and causing it to coincide at 
each reading with a set mark, by means of small weights of 
known value placed upon the platform, the reading being 
corrected accordingly. 

The thermometer also must be accurate and delicate; read- 
ing preferably (when possible) to tenths of a degree. 

The end of the supply pipe must be secured in the main 
pipe in such a way as to obtain as nearly as possible an average 
sample of the steam passing through the main steam pipe. 

The contents of the barrel during the test should be stirred 
(as pre-mentioned) thoroughly, to insure a uniform tempera- 
ture at the time the thermometer is read. 

By exercising good judgment, and paying due attention 
to all these matters of detail, the results should be within two 
per cent, of correct. 

The use of the barrel calorimeter has in many cases, however, 
been superseded by the throttling calorimeter, especially 
where very expert tests are necessary. 

An improved form of Separating Calorimeter, designed by 
Prof. R. E. Carpenter, is illustrated in Fig. 130, which has been 
in use in the laboratories of Sibley College and some other 
places for the past several years. 

The instrument may be described as follows : It consists 
of two vessels, one being inside the other ; the outer vessel 
surrounds the interior one in such a manner so as to leave a 
space between them which serves as a steam jacket; the in- 
terior vessel is provided with a water gauge glass 10, and a 
graduated scale 12. The sample of steam, the quality of which 
is to be determined, is supplied through the pipe 6, into the 
upper part of the interior vessel. 

The water contained in the steam is projected downward 
into the cup 14 together with the steam, where the course of 



And Its App lia n ces . 



255 



the steam and water is changed through an angle of nearly 180 
degrees, which causes the greater weight of water by its inertia 

to be thrown outward 
through the meshes in 
the cup and into the 
space 3 below in the 
inner chamber. 

The cup serves to 
prevent the current of 
steam from taking up 
any moisture which has 
already been thrown out 
by the force of inertia. 

The meshes in the 

cup project upward into 

the inside of the cup, so 

that the water intercepted will drip 

into the chamber 3, while the steam 




being deprived of a portion of its 
moisture, passes upward and enters 
the top of the outside chamber. 
From the outside chamber it is dis- 
charged through an orifice 8, in the 
bottom. This orifice is of known 
area, and is much smaller than any 
of the other passages through the 
calorimeter, consequently the steam 
in the outer chamber suffers no 
sensible reduction of pressure by 
passing through the instrument. 

The pressure being the same 
in both outer and inner chamber 
the temperature also remains the 
same ; therefore no loss by radiation 



256 Steam Engine Indicator 

can take place from the inner chamber except that 1 which 
occurs from the exposed surface of the gauge glass. The 
pressure in the outer chamber and also the now of steam in a 
given time is shown by a special graduated gauge attached 
to the instrument. 

The outer circle on the gauge dial is graduated by trial, 
and shows the weight of steam discharged in ten minutes of 
time at the observed pressure. The inner circle shows the 
pressure of steam in the outer chamber. 

By a law known as Napiers law, the flow of steam through 
an orifice from a higher to a lower pressure is in proportion to 
the absolute steam pressure, until the lower pressure equals or 
exceeds .6 of that of the higher. 

Careful experiments to test the correctness of this law has 
in all cases indicated its accuracy. 

The graduations of the scale 12 attached to the inner 
chamber show (when the index is properly set), the weight of 
water in pounds and graduated by hundredths which has been 
separated from the steam. 

This scale is graduated by actual calibration, making it as 
nearly correct as possible for the temperature of water cor- 
responding to a steam pressure of 100 pounds per square inch. 

The percentage of moisture in the steam is found by 
dividing the weight of water as shown by the water gauge 10, 
and scale 12, by the sum of this quantity and that shown on 
the gauge 9. The quality or percentage of dry steam is ob- 
tained by dividing the difference of the readings by thejr sum. 

The total size of the instrument is about 10x2^ inches, 
and its weight about six pounds. 



A nd Its Appliances, 257 



CHAPTER XXXI. 



MISCELLANEOUS DIAGRAMS. 



The diagrams illustrated in this chapter, some of which rep- 
resent an excellent distribution of the steam throughout the 
stroke, while others are quite the reverse, serve to indicate the 
beneficial results that may be attained by a proper use of the 
Indicator, and also by its use illustrates the progress made of 
late years in the distribution of steam in all types of engines. 
To a skilled engineer the diagram is an index to the steam 
economy of an engine, as it shows the action of the steam 
throughout the whole cycle of the pistons movement. 

It is a record of the steam from admission to exhaust, and no 
card can be considered complete which does not indicate every 
change from the time the steam enters the cylinder, until it is 
discharged either into the atmosphere, or the condenser. 

In treating a card from a compound or multi-cylinder expan- 
sion engine, the combined area of all the cards must be consid- 
ered, according to the scale of each, in order to ascertain the 
total power developed, and the cost of such power must be 
obtained from the terminal of the low pressure, or last cylin- 
der, as it is at this point that the useful work of the steam 
stops; consequently from here the cost must be obtained. 

It is an established fact that steam if expanded beyond a cer- 
tain limit in a single cylinder is accompanied by a loss in econ- 
omy ; therefore the only way to increase economy is by more 
cylinders and greater expansion ; hence our present tendency 
is to higher steam pressures and multi-cylinder engines. 



25« 



Steam Engine Indicator 



Fig. 131 represents a diagram taken from each end of a 
Fishkill Corliss Engine. Diameter of cylinder 20 inches by 48 




Fig. 131. 



inches stroke, revolutions per minute 58. Boiler gauge 84 lbs. , 
scale of spring 40. 




Fig. 132. 



Fig. 132 was taken from an automatic slow speed engine. 
Diameter of cylinder 20 inches, dia. of rod 3 inches, stroke 
48 inches making 63 revolutions per minute, 63 lbs. boiler 
pressure, scale of spring 32. 



And Its Appliances. 



259 



Figs. 133 and 134 were taken from the same pair of en- 
gines as the comparative diagrams represented in Chapter 
XXIV., the data of the engine being the same as there given. 




Fig. 133. 



In this case the horse power developed being greater than those 
in the previous chapter. 




Fig. 134. 



The horse power developed by the automatic Fig. 133, 
being 86.26 while that of the throttling engine, Fig. 134, is 
87.06. The mean effective pressure of each is 38 lbs. 



260 



Steam Engine Indicator 



Figs. 135 and 136 were taken from a side by side double 
Wheelock engine, cylinder 18 in. X48 in. stroke, running 54 
revolutions per minute, boiler pressure 90 lbs., the cranks con- 




Fig. 135. 



nected at right angles or quartering. The M. E. P. of Fig. 135 
being 32.2 lbs., and developing 101.75 horse power while the 
M. E. P. of Fig. 1 36 is 31.8 and developing 101.44 horse power. 




Fig. 136. 



Figs. 137 and 138 are diagrams from a Ball & Wood com- 
pound, high pressure cylinder 13 inches, and low pressure 



And Its Appliances, 



261 



cylinder 20^ inches by 15 inch stroke, running 270 revolu- 
tions per minute, boiler pressure 145 lbs. Scale of H. P. cyl. 
80, and L. P. cyl. 20. 




Fig. 137. 




Fig. 138. 

Figs. 139 and 140 are diagrams from a 14 in. x 14 In. Fitch- 
burg engine, revolutions 154 per minute. Boiler pressure 75 
lbs., by gauge. Scale 60. Fig. 139 shows the condition of an 



262 



Steam Engine Indicator 



engine when the indicator was first applied. Fig. 140 shows 
the improvement made, an increase of about 40 per cent, in 




Fig. 139. 




Fig. 140. 

mean effective pressure. The cuts are full size, and the load 
on the engine was 200 incandescent lamps of 16 c. p., and 39 
arc lamps, nominally 2000 c. p. 




Fig. 141. 
Fig. 141 are diagrams taken from both ends of a 13 in. x 13 



And Its Appliances. 



263 



in. Armington & Sims engine, 250 revolutions per minute 
Gauge pressure 85 lbs., and scale 50. 




Fig. 142. 




V 



<lr 



Fig. 143. 



Figs. 142 and 143 are diagrams taken from a Watts, Cam- 
bell tandem compound H. P. cylinder 18 inches, and low 



264 



Steam Engine Indicator 



pressure cylinder 32 inches by 42 inches, stroke running 100 
revolutions per minute. Boiler pressure 120 lbs. Scale H. P. 
60, and L. P. 10. 



(ft -u-eW*,, p. itf- SL'y'y -wv. 




Fig. 144. 

Figs. 144 and 145 were taken from a 7 in. x 12 in. Buckeye 
engine. The former was taken as found running, as per data 
on card. The latter was taken after the proper equalizing of 
the valve connections had been made. 




Fig. 145. 



Figs. 146 and 147 are diagrams from the high pressure 
cylinder of a Providence tandem compound engine, taken 
before and after adjusting. Diameter of cylinder 12 inches. 



A ?id Its Appliances. 



265 



Stroke 22 inches, revolutions per minute 175. Boiler pressure 
120 lbs. Scale 60. 







A 



Fig. 146. 



The improvement in Fig. 147 consisted in advancing the 
eccentric on the shaft, and equalizing the valve connections. 




A 



Fig. 147. 



Figs. 148 and 149 are diagrams from a Corliss condensing 
engine, with data affixed thereto. The improvement in Fig. 



266 



Steam Engine Indicator 



149 consisted of the same treatment as that given in the two 
preceeding diagrams. 




Iig. 248. 




Fig. 149. 



The diagrams Fig. 150 were taken from a Porter- Allen 
condensing engine, 13 inches diameter of cylinder, by 24 in- 
ches stroke, 200 revolutions per minute. Boiler pressure 80 
lbs. Vacuum 20 inches. 



And Its Appliances. 



267 



Diagrams, Fig. 151, were taken from a 14x24 x 14 inches 
Westinghouse compound engine, boiler pressure 120 lbs. 
Scale of Spring 60. 




2- 



Fig. 150. 
Fig. 152 shows a pair of diagrams (Photo reduced in size) 
taken from a compound tandem jacketed Corliss engine. 
Diameter of H. Pressure cylinder \6]/ 2 inches and L. Pressure 




Fig. 151. 
cylinder 32 inches; stroke 54 inches, revolutions per minute 
59. Boiler pressure 108 lbs. 



268 



Steam Engine Indicaior 



These diagrams shows the action of the steam while pass- 
ing through both cylinders, and it will be observed that the 
steam expanded from an initial pressure of 121 lbs. to 30 lbs. 
in the first cylinder, with an additional expansion in the 
second, or low pressure cylinder to 8 lbs., thus giving a range 
of temperature between 341 deg. and 182 degrees, a change of 
159 degrees. It is very evident that any attempt to get the 
same range of expansion from a single cylinder as obtained in 
this pair, would be attended with serious loss from condensa- 
tion ; hence, as higher steam pressures are used, and the num- 
ber of expansions increased, more cylinders are added in order 




r-. 










StUwC 2.<*. 






v__ 


ZZT" 


« 



Fig. 152. 

to keep the range of temperature in each cylinder within 
economical limits. Triple and Quadruple expansion engines 
are simply the results of high steam pressure, and more liberal 
expansion. 

The engines from wnich these diagrams were taken belong 
to the slow or medium speed type. 

In reference to indicator cards in general it will be seen 
that in many cases their lines do not reach that degree of excel- 
lence as shown in Fig. 152. 

The fault is often due to bad valve setting or poor valve 
construction, and it may sometimes be due to the indicator 
itself, either of which may cause the steam line to be wavy from 



And Its Appliances. 



269 



start to finish. The usual reason assigned, however, is the 
presence of water, which comes in such volume that its inertia 




Fig. 153. 




sc *i_ e. So 



Fig. 154. 
carries the indicator piston too far , but the chances are that if 
water passes in such quantities to the indicator, the engine will 



270 Steam Engine Indicator 

not escape some disaster, and as nothing unusual happens when 
such cards are taken it is fair to assume some of these irreeu- 
larities are due to other causes than water; one of which may 
be considered, and what appear to be the most logical cause. 

Diagrams Figs. 153 and 154 were taken from high speed 
engines, both taken at a speed of 350 revolutions per minute. 

The steam and expansion lines on Fig. 153 are all that can 
be desired; but the lines of Fig. 154 are quite irregular. 

On each diagram a circle is drawn to represent the travel 
of the crank pin. The element of time must be considered, 
and the influence it has on the indicator piston, spring, and 
pencil movement. All of the parts have weight, and conse- 
quently inertia. If the pencil movement is relatively slow, the 
inertia, or tendency to go too far, is slight and our diagram will 
be comparatively free from wave lines : on the contrary where 
the movement is rapid, or performed in an unusually short 
time, the inertia will be great and a diagram with irregular 
lines will be the result, as shown in Fig. 154. The valve 
motion of an engine influences this time, and in the cases of 
Figs. 153 and 1 54 there is enough difference in the valve motion 
to account for all the difference in the lines of the diagram. 

By referring to the diagrams it will be seen in Fig. 153 
that the indicator piston begins its upward motion at a point 
marked A on the exhaust line : at this time the crank is at A 
on the circle. If the compression line is followed it will be 
seen that when the indicator pencil arrives at the point B it has 
reached its limit of upward travel, and the crank has passed on 
to its point B through 92 deg. of the circle, or more than one- 
fourth of its entire travel. 

Here then is a high-speed engine so far as relative speed 
is concerned, but an easy speed for indicating ; because the 
large clearance, and early compression makes the movement 
of the indicator so gradual, that severe inertia shocks are elim- 
inated. 



And Its Appliances. 271 

Diagram Fig. 1 54 is lettered the same but there is a decided 
difference in the location of the letters. In this case compres- 
sion did not commence until the stroke was nearly finished, 
and only rose a few pounds. Ninety per cent, of the upward 
movement of the indicator pencil is represented by a nearly 
vertical line, showing that this motion occurred while the 
crank was passing through a very small part of its travel, that 
is, from A to B on the circle. 

If the difference in the spaces between the points A and B 
on the two crank circles be compared they will give a fair idea 
of the difference in the velocities of the pencil movement when 
these diagrams were taken. 

The difference is the measure of the disturbance, and in 
Fig. 153 will be found all the conditions which insure a smooth 
card, while Fig. 154 is decidedly the reverse. 

In indicator practice we occasionally get cards from slower 
running engines which show all the irregularities found in 
cards from high-speed engines : but an analysis of the diagram 
will probably show that the indicator has had but little help 
from compression, and the steam admission was very quick. 

Most of the excellent diagrams taken from high-speed 
engines, and published in the catalogues of indicator and engine 
makers, are usually from compression engines ; that is, the type 
which has large clearance and early compression. 

The diagram Fig. 155 is from a pump-cylinder scale 40, 
and the different lines represent all that can be desired ; as the 
nearest approach to a rectangle in a pump diagram, the better 
practice it represents. 

The line A is the atmospheric line, and the distance from 
that to the lower line represent the suction, which may be more 
or less, according to the height the water is lifted, and also to 
the freedom with which it passes to the pump. The upper 
line represents the pressure against the plunger or piston 
necessary to force the water out, and this pressure is due, and 



272 Steam Engine Indicator 

proportionate to the height to which the water is forced, and 
also to the friction it encounters in passing from the pump. 

Commencing at the right hand lower corner of the dia- 
gram, (the cylinder being full of water) and the piston begins 
to move, the pressure instantly rises to about 75 pounds above 
atmosphere, and continues at a uniform pressure to the end of 
the stroke, showing that there was no shock due to starting the 
water-column, and that the passage of the water from the pump- 




Fig. 155. 

cylinder was without additional resistance. If the cylinder is 
not filled with water, the line at the right will not be vertical. 
At the commencement of the return stroke the pressure 
instantly fell to 8^ pounds below atmosphere, the degree of 
vacuum necessary to lift the water The lower or suction- 
line is about as regular as the upper or discharge line showing 
with what freedom the water passes through the suction-valves. 
Such a diagram as this shows an absence of shock to the pump, 
and that a cylinder full of water is discharged at each single 
stroke. 



And Its Appliances. 



273 



Fig. 156 is a specimen of diagram which is often taken 
from pumps, and shows that enormous shocks take place to the 
parts as well as only partially filling the cylinder with water. 

This often happens in practice under circumstances, that 
cannot always be avoided, but in all cases our endeavors should 
aim to have the lines of a pump-diagram that will enclose a 
rectangular figure, and as such, it may be assumed that the 
operations of the pump must be satisfactory. If the construc- 
tion of the pump is such that tortuous passages exist, causing 
undue friction of the water getting into or out of the cylinder 




A 



Fig. 156. 

the shocks will be greater at some parts of the stroke than at 
others, and this will be shown by corresponding inclinations of 
the suction and discharge lines. Shocks and jars and inter- 
mittent action will be shown by abrupt irregularities in the lines 
as in Fig. 156. 

Fig. 157 represent diagrams taken from the steam cylinder 
of a Marsh pump working on a suction lift of 24 feet. 

By means of a deflecting valve, the exhausting end 
of the steam cylinder can, when desired, be placed in open 
communication with the suction chamber of the pump. The 
effect of this connection is to extend the vacuum existing in 



274 Steam Engine Indicator 

tire suction pipe to the exhaust side of the steam piston. To 
illustrate the value of this device as claimed for it, is the object 
of the above card. 

The full lines were traced with the steam exhausting 
directly into the atmosphere. The lever for operating the 
deflecting valve was then thrown over, thereby turning the ex- 
haust steam into the suction, and the indicator pencil again 
applied to the same card, thus tracing the dotted outline. 



WITH EXHAUST fT^AM OUT. 




WITH EXHAUST TURNED IN. 



scale of ur>::iriG<:-o. 




• VACUUM LINE 11 POUNDS. --" 

Fig. 157. 

From this it is apparent that the steam represented by the 
area enclosed between the upper full line, and the upper par- 
allel dotted line is just that much gain, for every stroke of the 
piston, (in this case nearly 25 per cent.), and it will be further 
noticeable that the total area enclosed by the dotted lines, ex- 
ceeds the figure enclosed by the full lines to a considerable 
degree, consequently, there is more power to perform the 
work, with a smaller expenditure of force, and with the labor 
a constant factor, the speed of the pump is increased, and a 
greater amount of water delivered. 



%k% 



And Its Appliances. 275 



CHAPTER XXXII. 



ENGINE ECONOMY. 



Iii considering the matter of steam economy in the engine 
alone, it must be understood that the Mean Effective Pressure of 
the steam acting against the piston for a given time, represents 
the exact measure or exponent of the work performed by the 
engine in such time, and is consequently an important factor 
in all calculations pertaining to engine performance. 

The Terminal Pressure, or that pressure of steam which 
would exist in the cylinder, provided the exhaust valve re- 
mained closed to the end of the stroke, is the corresponding 
measure or exponent of the consumption of steam or water by 
the engine, or the cost of the poiver, and is also an indispensable 
factor in the calculation of the diagram. 

But almost invariably in all makes of engines, the exhaust 
valve opens, and releases the steam before the piston reaches 
the end of its stroke ; and in such cases the Terminal Pressure 
is found by continuing the expansion curve in its gradually 
descending direction (by hand) to the end of the diagram, and 
measuring from that point to the vacuum line by the scale of 
the diagram, as shown at T. V., Fig. 77, page 159. 

From the conclusions conceded in reference to the Mean 
Effective and Terminal Pressures, it is evident that the maxi- 
mum economy will result when the mean effective pressure is 
greatest relatively to the terminal pressure ; therefore if by any 
means the former can be increased without a corresponding 



276 Steam Engine Indicator 

increase in the latter, or anything that will decrease the latter 
without correspondingly decreasing the former, must result in 
improving the economy of the engine. 

In non-condensing engines, therefore it would appear that 
the maximum economy with a given boiler pressure is theor- 
etically obtained when the full pressure is admitted to the cyl- 
inder and continued to such point of cut-off, as that the degree 
of resulting expansion may be such that at the end of the stroke, 
the terminal pressure has fallen to, or nearly to, atmospheric 
pressure. 

The attainment of this economy in practice will depend 
somewhat upon conditions, and the construction of the engine ; 
such as possessing a free exhast for the steam, in combination 
with the least possible loss from clearance, friction, leakage 
and condensation. 

Hence under favorable conditions it is possible to expand 
the steam until there is no more work in it, and no greater 
economy can be expected with a given initial pressure of 
steam ; unless by the aid of a condenser. 

With a given load, and boiler pressure, the best theoret- 
ical economy is obtained, when the cut-off takes place as early 
in the stroke, as is consistent with obtaining the average pres- 
sure in the cylinder to do the necessary work, and at the same 
time maintain the required speed of engine. 

The measure of the economy of the engine alone, therefore 
is the number of pounds of water which passes through the 
cylinder in the shape of steam per hour, for each indicated 
horse power developed. 

The actual amount of water thus consumed appears in 
three conditions ; and consists in part of the steam that begins 
to suffer condensation immediately upon leaving the boiler ; 
due to coming in contact with the comparatively cooler steam 
passages, and which is further increased upon striking the in- 
ternal surfaces of the cylinder ; part is condensed in the act of 



And Its Appliances. 277 

transforming- heat into work ; that is, in giving motion to the 
piston, and part in that discharged from the cylinder as ex- 
haust steam. 

The portion condensed in the act of changing heat into 
work is the only one of value ; as this quantity (namely, that 
exhausted and that whose heat is converted into work,) is the 
amount of water, or steam accounted for by the indicator, and 
is a measure of the performance of an engine, and when com- 
pared with the performance of the best, it shows the economy 
with which the engine works. 

The steam lost in internal condensation is not at all 
accounted for by the indicator. Hence the total amount of 
loss from this source is really the difference between the water 
actually pumped into the boiler, and that accounted for by the 
indicator. 

Tests. It is a very simple matter in testing a plant com- 
prising an engine and boilers, to ascertain the economy of the 
plant, as a zvhole, as theie is usually but little to determine 
beyond the quantity of fuel consumed, and the horse power 
developed ; but to ascertain the economy and the losses, aris- 
ing from each of the various parts of a plant, (such as the 
engines, boilers, heaters, economizers, pipes, etc.), requires 
close attention to all the several points to insure accurate 
results. 

Where tests of the latter kind are made the following par- 
ticulars and data should be recorded : 

First. The total weight of water supplied to the boiler. 

Second. The quantity of water drained from the separ- 
ator, (if one be used) which includes the water carried along 
with the steam ; (known as priming and for which the boiler 
alone is responsible) also the condensation in pipes. 

Third. The percentage of moisture in the steam that is 
being supplied to the engine. This may be determined by 



2 78 Steam Engine Indicator 



& 



means of what is called a calorimeter test, the method of its 
operation being described in Chapter XXX. 

From these amounts the weight of steam (or water) passing 
through the engine, per hour may be ascertained, and dividing 
this weight by the horse power developed will give the weight 
of steam used per horse power per hour. 

If this amount is very high it will probably be due to 
leakage, and if such should be the case it will be detected more 
quickly by this than by any other method. 

Fourth. The total weight of coal burned in the furnace. 

If this weight is small in comparison with the weight of 
water pumped into the boiler, showing a large evaporation per 
pound of coal, it will probably be found that the boiler primes. 

If the opposite of this is the case, it may be due to a poor 
quality of coal, improper firing, poor draft, etc., either of 
which will cause the final results to be disappointing, 

Fifth* The temperature of the feed water before and 
after passing through the heater ; this shows the efficiency of 
the heater. 

In a non-condensing engine the heating of the feed water 
by the exhaust steam should always be taken advantage of, as 
in this way a saving of coal will be effected of from 10 to 15 
per cent., depending upon the efficiency of the heater and 
manner of connecting. 

To realize the full economy from heating the feed water, 
it should not enter the boiler at a temperature less than 210 de- 
crees Fah. and besides, at this temperature it also obviates the 
strain on the boiler, that arises from feeding cooler water. 

In a condensing engine however there is but little gain 
from the use of a heater over that of feeding the boiler direct 
from the hot-well ; provided the temperature of the hot-well is 
not unnecessarily low; excepting under circumstances where 
the water used for condensing purposes is unfit for feeding the 
boiler on account of salt, lime, and other substances held in 



A nd Its Appliances . 279 

solution, and which causes such water to be deleterious in its 
action upon the interior surface of the boiler. 

In the latter case therefore, a slight economy may be de- 
rived from the use of a heater ; as by its use the fresh water 
selected for feeding the boiler may have its temperature con- 
siderably increased above that of the hot-well while passing 
through the pipes of the heater on its way to the boiler; and a 
somewhat further gain is effected, which consists in lessening 
the amount of water requisite to supply the condenser; due to 
the heater condensing a portion of the exhaust steam in its 
passage through it. 

In all steam plants there is considerable loss of heat from 
radiation, by the boiler and setting, and a large percentage of 
the fuel burned simply replaces the heat radiated from this 
source, such heat being conveyed away by the air passing over 
them, without doing any useful work in the way of forming 
steam ; and a further amount is also wasted by the radiation 
from the pipes, etc., between the boiler and engine, this latter 
causing the condensation of steam in the pipes. 

In order to have a test of this description complete, it is 
necessary that the amount of these losses from radiation be 
ascertained, as the heat radiated from the boiler and setting 
should not be charged against the steam formed ; the loss also 
from condensation in the pipes is an uncertain quantity and 
often much larger than supposed. 

One plan of ascertaining the amount of each of these 
losses is, after the engine has been stopped, to keep the nor- 
mal pressure of steam on the boiler for several hours, taking 
care to keep the water in the boiler, (as near as possible,) at 
the ordinary level, and the engine stop valve must be tightly 
closed to prevent any escape of steam or water through it. 

The amount of fuel burned, and also the quantity of water 
pumped into the boiler during this radiation test, should be 
carefully weighed, and at the end of the test the water of 



280 Steam Engine Indicator 

condensation must be drained from the engine steam pipe, and 
all other pipes connected directly with the steam space of the 
boiler, and this total amount also carefully weighed and noted. 

If during this test it is found that more water has been 
supplied to the boiler than that collected from the drains, the 
difference is evidently due to leakage ; therefore, when taking 
account of the steam passing k through the engine in a power 
test, this leakage should be allowed for. 

Hence, to ascertain the exact evaporation per pound of 
coal, it is necessary that the amount of coal burned, and water 
used per hour during the radiation test, be deducted from the 
coal and water used per hour during the power test. 

The difference in the amount of coal, shown by this sub- 
traction, is the actual amount that is consumed in forming steam 
only; while the difference in the amount of water used, shows 
the exact amount of water that has been formed into steam by 
this quantity of coal. 

Therefore, in power tests where the amount of coal con- 
sumed is the measure of the engine's performance, (as is fre- 
quently the case,) the quantity of coal remaining (after deduct- 
ing the amount used in the radiation test,) is the correct amount 
chargeable against the engine. 

In making the radiation test, every precaution should be 
taken that will tend to burn the coal to the best advantage ; the 
draft openings for the furnace, and also the back damper, 
should be carefully adjusted, so as to just maintain the pres- 
sure of steam required, and also to prevent an excess of air 
from conveying any large amount of heat up the chimney. 

In the absence of an accurate water metre for measuring 
the quantity of water forced into the boiler during a test, a 
very satisfactory arrangement may be substituted, consisting 
of two barrels or casks, in connection with an ordinary plat- 
form weighing scales. 



And Its Appliances. -281 

One of these barrels is placed upon scales, and together 
elevated above the second barrel, which for convenience, 
should be somewhat the larger. 

The feed water is drawn into and carefully weighed in the 
upper barrel, and then run off into the lower one, from which 
it is pumped into the boiler. 

Another and somewhat more convenient method of testing 
is sometimes resorted to, but which gives approximate results 
only. In this operation the feed water is brought to a given 
point near the upper part of the gauge glass, and then shut off, 
and the test made by observing the rate at which the water 
boils away. 

The height of the water in the glass at the beginning, and 
at the end of the test being carefully observed and noted. 

The weight of the water evaporated and supplied to the 
engine can then be calculated from the cubical volume that it 
occupied in the boiler, always bearing in mind that the weight 
of a given volume of water varies with its temperature. (See 
table No 9). 

To insure greater accuracy, tests made by this method can 
be repeated a number of times, and the results averaged. 

Feed water tests, made by measuring all of the water sup- 
plied to the boiler, are of no positive value unless leakage of 
water from the boiler (if any exist) be deducted therefrom ; 
hence, particular attention should always be given to this fact, 
and the leakage determined as before described. 

A better and more accurate way than either of the above 
methods for ascertaining the weight of steam consumed by an en- 
gine, is to use a Surface Condenser, in which all of the steam 
passing through the engine is condensed, and the resulting 
water saved and weighed ; and the only correction needed is 
to deduct the per cent, of moisture contained in the steam 
supplied, which may be determined by a Calorimetric test. 



.2.8-2 Steam Engine Indicator 

A portion of the steam required by an engine may also be 
found by calculation from the diagram. 

A method of making this calculation is given in Chapter 
.XXL ■ 

Engine economy includes everything that enters into cost 
of maintenance, and operation, and the problem with the en- 
gineer in charge of engines and boilers, is how to get the best 
possible results from such machinery as comes under his direc- 
tion. 

The value of his services depends largely upon his ability 
in this direction ,, and an important part of his education is 
how best to accomplish the most desired and economical re- 
sults. 

Economy to him consists in keeping. the fuel account as 
low as possible for the power developed, having few repairs, 
little loss (through accidents or otherwise) from stoppages, and 
also haying the least , possible loss from wear and tear or de- 
terioration. 

The cost of fuel is always an important matter, but some- 
times it happens of more importance that there be no com- 
pulsory stoppage of the engine or that the speed be very 
regular. 

It is the province of the engineer to study this in any par- 
ticular instance and govern himself according to circumstances 
and observation, and take measures to obviate or remove (if 
possible) whatever may be detrimental to good economy. 

In reference to fuel economy it frequently happens that 
the engineer has to contend with defective conditions, or under 
such adverse circumstances, as will render the attainment of 
good economy impossible. 

A condition very unfavorable to fuel economy of non-con- 
densing engines exists in cases where the expansion line of 
the indicator diagram falls below the pressure of the atmos- 
phere early in the stroke (as >showii ; mi Figr. 62), or in other 



A nd Its Appliances. 283 

words, where the engine is too large for its work, necessitating 
an early cut-off, and in consequence, greater loss from con- 
densation. 

The reason of this increased loss through condensation, 
is owing to the interior walls of the cylinder becoming cooled 
to a lower temperature during expansion and exhaust, and in 
consequence, a considerable portion of the entering steam at 
the beginning of the stroke is condensed ; due to parting with 
its latent heat in order to restore the temperature of the in- 
terior exposed surface of the cylinder. 

In an engine with a light load, the steam thus condensed 
is a larger proportion of the total steam used, than in one more 
heavily loaded. Another reason why poor economy is gener- 
ally the rule where light loads prevail, is that a part of the 
work done in the cylinder of a steam engine is in overcoming 
the /fiction of the moving parts; and this friction does not in- 
crease proportionately fast as the load is increased, the friction 
sometimes being nearly as great with light running, or no 
load, as with the engine fairly well loaded. 

In a non-condensing engine the useless work of moving 
the piston against the pressure of the atmosphere must always 
be done, besides some additional back pressure, although this 
will not increase as fast in proportion as the mean effective 
pressure is increased. In a condensing engine the piston has 
always to be moved against pressure due to imperfect vacuum, 
besides a certain amount of back pressure also. Owing to 
various conditions and circumstances, connected with the sub- 
ject, the exact loss from condensation cannot be ascertained 
very closely by calculation ; therefore it cannot be told just 
what the mean effective pressure on an engine piston should be, 
to realize the best economy in fuel consumption. 

Experiments to determine the relation of steam consump- 
tion to point of cut-off, under different pressures of steam in a 
non-condensing engine will be found described, in Chapter XXVI. 



284 Steam Engine Indicator 



CHAPTER XXXIII. 



The following table (No. 6) apply both to exhaust steam 
heaters and economizers where, what would otherwise be, waste 
heat is utilized for heating the feed water. 

The percentage of saving given is the saving in the amount 
of heat required to generate a certain quantity of steam. The 
saving in fuel depends on other conditions, and may be more 
than given above. If, for instance, a boiler is too small to 
steam easily without a feed-water heater, the application of a 
heater will make a much greater saving in fuel than the per- 
centage given in the table : but if the boiler steams easily with- 
out a heater, the addition of a heater will save about the same 
per cent, of fuel as given in the tables. It is assumed in each 
case that the addition of an exhaust steam heater does not im- 
pair the vacuum on a condensing engine, or increase the back 
pressure on a non-condensing engine, and that the addition of 
an economizer does not impede the draught. 

A heater may be applied to the exhaust pipe of a condensing 
engine that will, without impairing the vacuum, heat the feed- 
water from the temperature of the hot well (about ioo°)to 165 or 
170 , a saving of about 6 per cent., then passing it through an 
economizer, should raise the temperature another ioo° (from 
170 to 270 ), making a further saving of about 10 per cent. 

In non-condensing engines an exhaust steam heater will 
heat the feed-water from 62 to 210 , a saving of 12.9 per cent. 

An economizer will heat the feed-water to from 220 to 
320 , according to the temperature of the waste gases, and also 
the temperature of the water entering the economizer. 



A nd Its Appliances. 285 

After heating the water, care should be taken that it stays 
hot until it enters the boiler. If, for instance, the water is 
heated in an economizer to 270 , and then in passing through 
the pipes to the boiler it cools down io°, to 260 , there is a loss 
of 1.06 per cent., the greater portion of which might be saved 
by carefully protecting the pipes. 

The temperature of the feed water, before and after passing 
through the economizer, and the temperature of the gases 
both sides of it, will show whether the economizer is efficient 
or not. If the temperature of the water leaving the economizer 
gradually lowers while the average temperature of the escap- 
ing gases gradually increases, it indicates a scaling up of the 
economizer, which at once requires attention. Also if the 
quantity of fuel increases gradually, it may possibly be due to 
air leaks in the setting or scaling either in the boiler, or econ- 
omizer, and should be remedied. 



2T86 



Steam "Efigine Indicator 



Table No.. 6. 



Saving effected by the use of Feed-Water Heaters in the generation of steam of ioo lbs. guagt 
pressure or 115 lbs. total pressure. .. - 



Temp, 
from 


Temperature of the Water entering Boiler. 


which the 
water is 


32° J 33° | 40° | 43° ) 30° | 33° | 


60" I 62° | 63> | 70° | 73° | 80° | 83"' 


heated 
or cooled. 


Percentage of gain (-H or loss 


( — ) by heating or cooling the water. 






+ 


+ 


+ 


+ 


+ 


+ 


-r 


+ 


+ 


+ 


+ 


+ 


32° 


00 


•25 


•67 


110 


1-52 


1-94 


2-36 


253 


2-79 


321 


3-63 


4-05 


447 


35 


-'25 


•00 


•42 


•85 


127 


1-69 


212 


2-29 


254 


296 


3-39 


3-81 


4-23 


40 


•67 


-•42 


•00 


•43 


•85 


1-28 


1-70 


.1-87 


2-13 


2-55 


298 


340 


383 


45 


110 


•85 


-•43 


*00 


•43 


•85 


1-28 


145 


171 


213 


256 


2-99 


341 


50 


152 


1-27 


•85 


— •43 


•00 


•43 


'86 


1:03 


1-29 


1-71 


214 


2-57 


300 


55 


1-94 


1-69 


1-28 


•85 


-•43 


•00 


•43 


•60 


•86 


1-29 


1-72 


215 


2-58 


60 


236 


212 


1-70 


1-28 


*86 


-•43 


fc '00 


17 


•43 


•86 


1-30 


1-73 


216 


62 


253 


2-29 


1-87 


145 


103 


•60 


-17 


•00 


•26 


•69 


113 


1-56 


199 


65 


279 


254 


213 


1-71 


1-29 


•86 


•43 


-•26 


•00 


43 


•87 


1-30 


1-74 


70 


321 


296 


2'55 


213 


1-71 


1-29 


•86 


•69 


-•43 


•00 


•44 


•87 


1-31 


75 


363 


339 


298 


256 


214 


1-72 


130 


T13 


•87 


-44 


•00 


•44 


•88 


80 


405 


381 


340 


2-99 


257 


215 


1-73 


156 


1-30 


•87 


-•44 


•00 


•44 


85 


4-47 


4-23 


383 


341 


300 


258 


216 


1-99 


1-74 


1-31 


88 


-•44 


•00 


90 


490 


466 


4-26 


385 


3-44 


302 


2-60 


243 


2-18 


1-75 


132 


•89 


-•45 


95 


533 


5 09 


468 


428 


387 


345 


304 


2-87 


261 


219 


1-76 


1-33 


•89 


100 


575 


5-51 


511 


470 


430 


3-88 


347 


330 


305 


263 


2-20 


1-77 


1-33 


110 


659 


636 


5-96 


556 


515 


474 


4-33 


417 


392 


3-50 


307 


265 


222 


120 


7-44 


720 


6-81 


6-41 


601 


560 


520 


503 


4-79 


437 


395 


353 


310 


130 


8-29 


8-06 


7-67 


727 


6'88 


6-47 


6-07 


591 


566 


525 


434 


4-42 


4-00 


140 


914 


880 


852 


813 


773 


733 


693 


677 


653 


612 


571 


530 


4-88 


150 


9-99 


976 


938 


899 


8-60 


8-20 


7-81 


765 


741 


700 


660 


619 


577 


160 


1084 


10-61 


1023 


985 


9-46 


907 


8-68 


852 


8-29 


7-39 


7 48 


707 


666 


170 


1168 


11-46 


1108 


10-70 


1032 


9-93 


955 


939 


915 


8-76 


836 


795 


755 


180 


1254 


1231'H 94 


11-57 


11-19 


10-80 


1042 


10-26 


10-03 


9-64 


924 


8-84 


8-44 


190 


1339 


1317 1280 


1243 


12-05 


11-67 


11-29 


11-14 


10-91 


1052 


1013 


9-73 


9-33 


200 


1424 


1402 1366 


1329 


12-92 


L2-54 


1217 


12-01 


11-79 


1140 


1101 


1062 


1023 


210 


15-10 


1489 


1453 


1416 


13-79 


1342 


1305 


1290 


12-67 


12-29 


11-91 


1152 


1113 


212 


1527 


1506 


14-69 


1433 


13-96 


13-59 


13-22 


13-07 


12-85 


1247 


1208 


11-69 


1130 


220 


1596 


15-74 


15-38 


1502 


14-66 


1429 


13-92 


1377 


1355 


13-17 


12-79 


12-41 


12 02 


230 


1681 


1660 


16-24 


1589 


15-52 


1516 


14-79 


14-65 


1442 


14-05 


13-68 


13 30 


1291 


240 


1766 


1745 


1710 


1675 


16-39 


1603 


1567 


15-52 


1530 


1493 


14-56 


1418 


13-81 


250 


1852 


18-32 


17-97 


1762 


17-26 


16-91 


1655 


1641 


1619 


15 82 


1545 


15 08 


14-71 


260 


1938 


19-18 


18 83 


1849 


1814 


17-78 


1743 


17-29 


17 0; 


1671 


1635 


1598 


1561 


270 


2024 


20-03 


1969 


1935 


1901 


1866 


18-31 


1817 


17 95 


17 59 


1723 


1687 


1650 


280 


2109 


20-89 


20-55 


2021 


19-87 


1952 


1918 


1904 1883 


1847 


1812 17-76 


1739 


290 


2195 


2175 


2142 


21-08 


20-75 


20-40 


2006 


19-92 19-71 


19-36 


1901 1865 


18'30 


300 


22-80 


22-61 


2228 


21-95 


21-61 


21-27 


20-93 


20-8020-59 


20 25 


19- JO 


1954 


1919 


310 


2367 


2347 


2314 


22-82 


22-49 


2215 


21-82 


21-68 21 48 


2114 


20-79 


20-44 


20-09 


S20 


24-52 


2432 


2400 


2368 


2335 


2302 


22-69 


22 56 


22-35 


2202 


21-67 


21-33 


20-98 



And 7/s Appliances. 
Table No. 6.— Coxttntjed. 



2S7 



Saving effected by the use of Feed- Water Heaters in the generation of steam of ioo lbs. guig'e 
pressure or 115 lbs. total pressure. 



Temp, 
from 


Temperature of the Water entering Boiler. 


which the 
water is 


90° j 93° | 100° | liO J 1 120" | 130° | 140° | 130° | 160° | 170°, | 180° | 190° | 200° 


heated 
or cooled. 


Percentaee of gain ( +) or loss (— ) by heating or cooling the water. 




+ 


+ 


+ 


+ 


+_ 


+ 


+ 


+ 


+• 


+ 


+ 


+ 


+ 


32° 


490 


533 


575 


659 


7-44 


8-29 


9-14 


9-99 


10.-84 


11-68 


12 54 


1339 


1424 


35 


466 


509 


551 


636 


7-20 


806 


8-80 


9-76 


10-61 


11-46 


1231 


13 17 


1402 


40 


4-26 


468 


511 


596 


681 


7-67 


852 


938 


10-23 


1108 


1194 


12-80 


1366 


45 


385 


428 


470 


5-56 


6-41 


7-27 


813 


8-99 


985 


10-70 


1157 


12 43 


13 29 


50 


344 


3 87 


4-30 


515 


6-01 


6-88 


773 


8-60 


. 946 


10-32 


1119 


12 05 


1292 


65 


302 


345 


3-8S 


474 


560 


647 


733 


8-20 


9-07 


9-93 


1080 


1167 


1254 


60 


2-60 


304 


347 


433 


5-20 


6-07 


693 


7-81 


8-68 


955 


10 42 


1129 


1217 


62 


2 43 


287 


330 


4 17 


5 03 


5-91 


6-77 


765 


8-52 


939 


1026 


1114 


12.01 


65 


2-18 


261 


3 05 


392 


4-79 


566 


6-53 


741 


8-29 


915 


10 03 


10-91 


1179 


70 


1-75 


219 


2-63 


350 


4-37 


525 


6-12 


7-00 


7*89 


876 


964 


1052 


11-40 


75 


132 


176 


220 


307 


395 


4-84 


571 


660 


7*48 


836 


924 


1013 


11-01 


80 


•89 


1 33 


177 


265 


353 


'4-42 


5-30 


619 


7-07 


795 


884 


973 


10-62 


85 


•45 


•89 


133 


222 


3-10 400 


4-88 


577 


6-66 


755 


8 44 


933 


10-23 


90 


•00 


•44 


•89 


l - 78 


266 356 


445 


534 


6-24 


713 


802 


892 


982 


95 


-44 


•00 


•45 


134 


223 313 


402 


4-92 


582 


6-71 


7-62 


.852 


942 


100 


•89 


-45 


•00 


•90 


1 : 79| 2-70 


s 359 


450 


'5-40 


6-30 


7-20 


8-11 


901 


110 


1-78 


134 


-90 


•00 


•90 


1-82 


2-72 


363 


455 


545 


636 


7-28 


8-19 


120 


2-66 


223 


179 


-•90 


•00 


•92 


1-83 


275 


3-68 


4'59 


551 


643 


735 


130 


356 


313 


2-70 


182 


-•92 


•00 


•92 


1-85 


2-78 


370 


463 


556 


649 


140 


445 


402 


359 


2-72 


1-83 


-•92 


•00 


•94 


1-88 


281 


374 


4 68 


562 


150 


534 


492 


4-50 


3-63 


2-75 


1-85 


-•94 


•00 


•95 


1-89 


283 


378 


473- 


160 


624 


5-82 


5'40 


4-55 


368 


278 


1-88 


-95 


•00 


•95 


1-90 


286 


382 


170 


713 


671 


630 


5-45 


4-59 


3-70 


2-81 


1-89 


-•95 


00 


•97 


1-93 


290 


180 


802 


7-62 


720 


636 


•5-51 


4-63 


374 


2-83 


1-90 


-97 


•00 


•97 


1-95 


190 


892 


8-52 


811 


7-28 


6-43 


5-56 


'4-68 


378 


2-86 


1-93 


-97 


•00 


98- 


200 


982 


942 


901 


8-19 


735 


6-49 


5:62 


473 


382 


290 


195 


-•98 


00 


210 


1072 


1032 


9-93 


911 


8-28 


743 


6-57 


5-68 


478 


387 


2 93 


198 


-100 


212 


1090 


1051 


1010 


9-29 


8-46 


7-61 


6-75 


5-87 


4-97 


406 


3 13 


217 


1-20 


220 


1162 


11-23 


1083 


1002 


9-20 


£•36 


751 


663 


5-74 


4-84 


391 


2 95 


200 


230 


1252 


1213 


11-74 


1094 


10-12 


929 


8-44 


7-58 


669 


580 


4-88 


395 


299 


240 


1342 


13-03 


12-64 


11-85 


1104 


10-22 


938 


8-52 


765 


677 


586 


493 


399 


250 


1432 


1394 


1355 


12-77 


11-97 


1116 


10-33 


948 


862 


7-74 


684 


593 


4 99 


260 


1522 


1485 


14-47 


1369 


1291 


12-10 


11-28 


1044 


958 


8-72 


7-83 


692 


600 


270 


1612 


1575 


1537 


14-61 


1383 


1303 


12-22 


11-39 


10-54 


968 


8-80 


790 


699 


280 


1702 


16-65 


1628 


15-52 


1475 


1396 


13-16 


1233 


11-50 


1065 


978 


889 


798 


290 


17 92 


17 56 


1719 


16-44 


1568 


14-90 


14-10 


13-29 


1246 


11-62 


1076 


988 


899 


300 


18 82 


1846 


1809 


1736 


16-601582 


1504 


1424 


1342 


1259 


1174 


10 87 


998 


310 


19 73 


1937 


1901 


18-28 


1753 1676 


15-99 


1519 


1438 


13 57 


1272 


1186 


10 99 


320 


2062 


2027 


1991 


1919 


1845 


1769 


1693 


1614 


1534 


14 53 


1370 


12 85 


11-9& 



Steam Engine Indicator 



Table No. 6.— Continued. 



Saving effected by the use of Feed-Water Heaters in the generation of steam of ioc lbs. guage 
pressure or 115 lbs. total pressure. 



Temp. 

from 

which the 

water is 

heated 

or cooled. 



Temperature of the Water entering Boiler. 



32° 

35 

40 

45 

50 

55 

60 

62 

65 

70 

75 

80 

85 

90 

95 

100 

110 

120 

130 

140 

159 
160 
170 
180 
190 
200 
210 
212 
220 
230 

240 
250 
260 
270 

280 
290 
300 
310 
220 



I 212° J 220° I 230° | 240° | 230° | 260° | 270° | 280° | 290° | 300° | 310° | 320° 



Percentage of gain (+) or lossj( — ) by heating or cooling the water. 



151C 

14 

1453 

1416 

13 79 

1342 

1305 

1290 

1267 

12 29 

1191 

1152 

1113 

10 72 

10-32 

993 

911 

828 

743 

657 

5*68 
4-78 
387 
293 
1-98 
1-00 

•00 

-•21 
1-00 
201 

301 
403 
504 
605 
705 
806 
9-07 
1009 
11-09 



+ 
1527 
1506 
14 69 
1433 
13 96 
13 59 
13 22 
13 07 
1285 
1247 

1208 

1169 

11:30 

1090 

1051 

10-10 

929 

846 

761 

675 

5-87 

4 97 

406 

313 

217 

1-20 

•21 

•00 

-•81 

1-81 

2'82 
384 
4-85 
586 
tf-87 
7-88 
8-89 
9 91 
1091 



+ 

1596 

1574 

15 38 

1502 

14-66 

14 29 

13 92 

1377 

1355 

1317 

1279 

1241 

1202 

11-62 

11-23 

10-83 

1002 

920 

8'36 

751 

663 

574 

4-84 

391 

295 

200 

100 

•81 

•00 

-1-01 

203 
305 
4'08 
509 
611 
713 
814 
917 
10.19 



+ 

1681 

1660 

16 24 

15 89 

1552 

1516 

1479 

1465 

1443 

1405 

1368 
1330 
12 91 
1252 
1213 
1174 
1099 
10 12 
9 29 
844 

7-58 
669 
5 80 
4-88 
3'95 
2-99 
201 
1-81 
1-01 
'W 

•1-03 
206 
310 
412 
515 
618 
721 
824 
9 27 



1766 
1745 
1710 
16 75 
1639 
1603 
1567 
1552 
1530 
1493 

1456 
1418 
1381 
1342 
1303 
1264 
ir85 
11-04 
10 22 
9'38 

852 
7 65 
6-77 
5-86 
4-93 
399 
3 01 
282 
2-03 
103 

•00 
■l!05 
2-09 
313 
416 
521 
625 
729 
833 



18-52 
1832 
1797 
1762 
1726 
1691 
1655 
1641 
1619 
1582 

15 45 
15-08 
14-71 
1432 
1394 
1355 
12*77 
U97 
11-16 
1033 

948 
8-62 
774 
684 
593 
499 
403 
384 
3'05 
206 

105 

•00 

-1-06 
210 
315 
421 
525 
631 
7 36 



1938 
1918 
1883 
1849 
1814 
1778 
1743 
1729 
1707 
1671' 
I 
1635 
1598 
1561 
1522 
14-85! 
14-47' 
1369 
1291 
1210 
11-28 



+ 1 + 
2024 2109 
20 03 2089 
19 69 2055 
19-35 20 21 
19-01 19 87 
18-66 1952 
1831 ! 1918 
1817 1904 
17-95 1883 
1759 1847 



1723 
16 87 
1650 
1612 
1575 
1537 
1461 
13 83 
1303 
1222 



10-44'll-39 


958,10-54 


872 


9 68 


7-83 


8 80 


6-92 


790 


600 


699 


5-04 


605 


4-85 


586 


408 


5-09 


310 


412 


209 


313 


1-06 


210 


•00 


106 


-106 


•00 


212 


-107 


318 


215 


424 


322 


531 


4-30 


637 


537 



1812 
1776 
1739 
17 02 
1665 
1628 
1552 
1475 
1396 
1316 

1233 
1150 
1065 
978 
889 
7'98 
705 
687 
6-11 
515 

4-16 
315 
2-12 
1-07 
•00 
-109 
217 
325 
4:34 



6519 



2195 
2175 
2142 
2108 
2075 
2040 
20 06 
19-92 
19 71 
1936 

19 01 

18 

1830 

1792 

1756 

1719 

1644 

15 68 

14-90 

1410 

13 29 

1246 

11-62 

10-76 

9-88 

899 

8-06 

7-88 

713 

6-18 

521 
421 
318 
215 
1-09 
•00 
-109 
2-20 
329 



2280 
2261 
2228 
2195 
2161 
2127 
2093 
20 80 
20 59 
2025 



23:67 
23:47 
23*14 
22-82 
22'49 
2215 
2182 
21-68 
2148 
2114 



1990 20 
54 20' 
1919 20 



18-82 
1846 
1809 
1736 
1660 
1582 
1504 

1424 

1342 

12-59 

1174 

1087 

998 

907 

8-89 

8-14 

721 

625 
525 
4-24 
3'22 
217 
109 
. -00 
-112 
222 



1519 

14-38 

1357 

1272 

11-86 

10-99 

10-09 

991 

917 

824 

729 
631 
531. 
4-30 
325 
220 
112 
•00 
-112 



+ 

2452 

2432 

2400 

23-68 

2335 

23-02 

2269 

22 56 

22 35 

22-02 

2167 
2133 
20-98 
2062 
2027 
19 91 
1919 
18*45 
1769 
1693 

16-14 
15-34 
14-53 
1370 
12-85 
11-99 
1109 
1091 
10'19 
9-27 

8-33 
736 
637 
537 
4-34 
329 
222 
112 
00 



And Its Appliances. 



289 



Table No. 7. 

Areas and Circumferences of Circles from 164 to 4 inches in diameter varying by sixteenths* 
and from 4 inches to 100 inches varying by one-eighth inch. 





















Diam. 


Area 


Circum. 


Diam. 


Area 


Circum. 


1 Diam. 


Area 


Circum. 


in 


in Square 


, in 


in 


in Square 


in 


1 in* 


in Square 


in 


Inches. 


Inches. 


inches. 


Inches. 


Inches. 


Inches. 


llnches. 


Inches. 


Inches. 


•A 


O.OOOI9 


O.0490 


3 7<r 


7.3662 


9.62H 


18 3 
I 8-8 


55-088 


26.3I 


-h 


O.OOO76 


O.095I 


•i 


7.6699 


9-8175 


_1 


56.745 


26.70 


t 


O.OO306 


O.1963 


3 


7.9798 


IO.OI38 


58.426 


27.IO 


O.OI22 


O.3927 


•4 


8.2957 


10.2102 


I '* 


60.132 


27.49 


•p 


O.0276 


O.5890 


5 

•TS 


8.6179 


IO.4065 


61.862 


27.88 


•4 


O.0490 


O.7854 


3 
'8 


8.9462 


IO.6029 


9- 


63.617 


28.27 


5 

'TS 


O.0767 


O.9S17 


•TV 


9.2806 


IO.7992 




65-396 


28.66 


3 

• 8 


0.1 104 


I.17S1 


* 


9.621 I 


IO.9956 


'' 


67 20O 


29.06 


•T 7 S 


0.1503 


1-3744 


•TS 


9.9678 


II.I919 


•8 


69.029 


29-45 


'\ 


0.1963 


1.5708 


•f 


IO.3210 


II.3883 


9 'k 


70.882 


29.85 


•TS 


0.2485 


1-7671 


1 1 
■Tg 


IO.6796 


II.5846 


9 .§ 


72-759 


30.24 


■fl 


0.3067 


1.9630 


2 

"4 


IO.9446 


II. 7810 


a 

I 


74.662 


3063 


I! 


0.3712 


2.1590 


_3 


II.4159 


"•9773 


76.588 


31.02 


0.4417 


2.3565 


2. 

•8 


II.7932 


12.1737 


jio. 


78.540 


3 1 42 


.?! 


0.5174 


2-5512 


•« 


12.1763 


12.3700 


JL 

■8 


80.515 


31.81 


■f. 


0.6013 


2-7490 


4- 


12.566 


12.57 


■4 


82.516 


3220 


1 5 

-TS 


0.6902 


2-9453 


•4 


I3-364 


12.96 


1 


84.540 


3259 


I. 


0.7854 


3.1416 


14.186 


13-35 




86.590 


32-99 


TS 


0.8861 


3-3379 


3 

•8 


I5.033 


13-74 


■1 


88.664 


33.38 


"t 


0.9940 


3-5343 


* 


I5.904 


14.14 


a 


90.762 


33-77 


3 
• 1 


I 1075 


3-73o6 


16.800 


J4-53 


92-885 


34.16 


•4 


I 2271 


3.9270 


•t 

•8 


17.720 


14.9 2 


11. 


95 033 


3456 


•T 5 o 


'•3529 


4.1233 


18.665 


15-32 


JL 

•8 


97 205 


3495 


•1 


1.4848 


4-3197 


5- 


I9635 


15-71 


| 


99.402 


:>r>-3A 


•T 7 S 


1.6229 


4.5160 


•i 


20.629 


16.10 


101 62 


35-74 


A 


1.7671 


4.7124 


1 
•4 


21.648 


16.49 


•£ 


103.87 


36.13 


•P 


1-9175 


4.9087 


4 


22.690 


16.89 


•"8 


106.14 


3652 


■f 


2.0739 


5-1051 


4 


23-758 


17.28 


:| 


108.43 


3691 


: ?i 


2.2365 


5-3oi4 


•1 


24.850 


17.67 


110.75 


37-31 


2.4052 


5-4978 


•f 

•8 


25-967 


18.06 


12. 


113.10 


37-7Q 


°"H 


2.5801 


5.6941 


27.I08 


18.46 


"'* 


115.47 


38.09 


7 


2.7611 


5-8905 


6. 


28.274 


18.85 


•4 


117.86 


38.48 


1_5 
• 1 6 


2.9483 


6.0868 


■4 


29.464 


19.24 




1 20. 23 


38.88 


2. 


3.1416 


6.2832 


1 
•4 


30.680 


19.64 


.1 


122.72 


39-27 


•f 


3-34" 


6-4795 


•1 


3I-9I9 


20.03 


•0 


125.18 


39-66 


3-5468 


6.6759 


.1 


33-I83 


20.42 


a 


127.68 


40.06 


•T 3 6 


3-7582 


6.8722 


•1 


34-471- 


20.81 


130.19 


40.45 


•4 


3.9760 


7.0686 


a 

•7 

•8 


35-785 


21.21 


13. 


132.73 


40.84 


.- 5 -*- 


4.2001 


7.2649 


37.122 


21.60 


•f 


135.30 


41-23 


i 


4.4302 


7.4618. 


7- 


38.484 


21.99 


i 

•8" 


137.89 


41.63 


-A 


4.6664 


7-6576 


■4 


39-871 


22.38' 


140.50 


42.02 


f K 


4.9087 


7.8540 


1 
•4 


41.282 


22.78 




143.14 


42.41 


•I 9 ? 


5-1573 


8.0503 


•8 


42.718 


23-17 


•1 


14580 


42.80 


•* 


5-4II9 


8.2467 


J. 

:| 


44-179 


23-56 


:1 


148.49 


43.20 


1 ! 


5-6727 


8.4430 


45-663 


23-95 


151.20 


43-59 


2 

•4 


5-9395 


8.6394 


3 

1 


47.173 


24-35 


14. 


15394 


43-98 


•it 


6.2126 


8.8357 


48.707 


24.74 


•i 


156.70 


44-38 


•8" 


6.4918 


9.0321 


8. 


50.265 


2513 


:| 


159-48 


44-77 


•if 


6.7772 


9.2284 


i 


51^848 


25-52 


162.29 


45.16 


3- 


7.0686 


9.4248 


•4 


53456 


25.92 


.* 


165.13 


45-55 



290 



Steam 



Engine 



Indicator 



Table No. 7. — Continued. 

Areas and Circumferences of Circles from 1-64 to 4 inches 1:1 diameter, varying by sixteenths; 
and from 4 inches to 100 inches varying by one-eighth inch. 



Di 


am. _ Area 


Circum. Di 


im. Area 


Circum. | Diam. 


Area 


Circum. 


: 


n in Square 


in 1 


n in Square 


in 1 


n 


in Square 


in 


Inc 


hes. Inches. 


Inches. Inc 


hes. Inches. 


Inches. Pinches. 


Inches. 


Inches. 


14 


f 167.99 


45-95 21 


1 358.S4 


67 15 28 


k 


621.26 


88.36 




| 17087 
! 173.78 


46.34 


i 363-05 


67.54 


1 
4 


626.80 


88.75 




46.73 


f 367-2S 


67.94 


3 

8 


632.36 


89.14 


15 


176.71 


47-12 


| 371-54 
1 375-83 


68.33 


2 


637 94 


89-54 




& I79-67 


47-52 


6S.72 


1 


643-55 


S9-93 




i 182.65 


47 91 22 


330.I3 


69.12 


3 
4 


649.18 


90.32 




| 18566 


48.30 


& 384.46 


69-51 


i 


654.84 


90.71 




£ i S3. 69 


48.69 


i 388.82 


69.90 a 29 




660.52 


91.11 




1- 191-75 


49.09 


1 393- 20 


70.29 i 


^ 


666.23 


91.50 




| I94-83 


49.48 1 


1 397-61 


70.69 B 


1 
4 


671.96 


91.89 




.i 197-93 


49-87 I 


$■ 402.04 


71.08 8 


■i 
8 


677 71 


92.28 


16 


201.06 


50.27' 


f 406.49 
§ 410.97 


71.47 s 


1 

2 


683.49 


92.68 




i 204.22 


50.66 


71.86 1 


1 


689.30 


93-°7 




i 207.39 


51-05 23 


415.48 


72.26 


3 

i 

3 


695-I3 


93-46 




^ 210.60 


51-44 


* 420. 


72.65 


700.98 


93-85 




i 213.82 


51.84 


1 424.56 


73-04 30 




706.86 


94-5 




$ 217.08 


52.23 


1 429.I3 


73-43 


i 


712 76 


94.64 




| 220.35 


52.62 


* 433-74 
I 438.36 


73.83 


4 


718.69 


95-03 




1 223.65 


53-oi 


74- 2 2. 


8 


724.64 


95-43 


17 


226.98 


53-41 


| 443-OI 
i 447-70 


74.6i 


t 


730.62 


95.82 




* 230.33 


53-8o 


75- 


t 


736.62 


96.21 




£ 233.70 


54-19 24 


452.39 


75.4o 


a 


742.64 


96^60 




•a 237 10 


54-59 


* 457 11 


75-79 


| 


743.69 


97- 




k 240.53 


54.98 


\ 461.86 


76.18 31 
76.53 




754-77 


97-39 




.* 243.98 


55-37 


| 466.64 


1 


760.S7 


97 78 




.f 247.45 
i 250.95 


55.76 


h 471.44 
1 476.26 


76.97 


1 
4 


766.99 


98.17 




56.16 


77.36 


1 


773-14 


98.57 


iS 


254-47 


56.55 | 


f 481.11 
I 485.98 


77.75 


^ 


779-31 


98.97 




& 258.02 


56.94 1 


78.15 


I 


785-5I 


99-35 




i 261.59 


57-33 1 25 


490.87 


78.54 


3 

1 

8 


791-73 


99-75 




f 265.18 


57-73 


£ 495.8o 


78.93 


797-93 


100.14 




£ 268.80 


58.12 


£ 500.74 


79-33 S32 




804.25 


100.53 




i 272.45 


58.51 


I 505.71 


79.72 


1 

8 


810.54 


100.92 




I 276.12 
1 279.81 


58.90 


* 510.71 


80,11 I 


JL 


816.86 


101.32 




59-3° 


i 515.72 


80.50 


1 


823.21 


101.71 


19 


283.53 


59-69 


1 520.77 
1 525.84 


80.90 


! 


829.58 


102.10 




i 287.27 


60.08 


81.29 


835-97 


102.49 




i 291.04 


60.48 26 


530.93 


81.68 


a 

i 


842.39 


102.89 




f 294.83 


60.87 


h 536.05 


82.07 


848.83 


103.28 




i 298.65 


61.26 


I 541.19 


82.47 33 




855-30 


103.67 




1 302-49 


61.65 


I 546.36 


82.86 


i 


861.79 


104.06 




1 306.35 
s 3 IO - 2 5 


62.05 


i 551.55 
t 556.76 


83.25 


4 


868.30 


104.46 




62.44 


83.64 


a. 


874.84 


104.85 


20 


314.16 


62.83 


t 562. 


84.04 


X 


881.41 


105.24 




& 318.10 


63.22 


I 567.27 


84.43 


1 


888. 


105.64 




£ 322.06 


63.62 27 


572.56 


84.82 


§ 


894.62 


106.03 




f 326.05 


64.01 


i 577-87 


85.21 


£ 


901.25 


106.42 




I 33o.o6 


64.40 


£ 583.21 


85.61 34 




907.92 


106.81 




f 334- 10 


64.79 


f 588.57 


86. 


$ 


914.61 


107.21 




f 338.16 
1 342.25 


65-19 


| : 593-96 


86.39 


1 

4 


921.32 


107.60 




65.58 


# 599-37 


86.79 


1 


928.06 


107.99 


21 


346.36 


65-97 


| 604.81 
| 610.27 


87:18 


h 


934-82 


108.39 




& 350.50 


66.37 


87.57 


# 


941.60 


108.78 




i 354-66 


66.76 28 


615.75 


,87.96 


3. 
4 


948.42 


109.17 



And Its Appliances 



: 9 l 



Table No. 7. — Continued. 

Areas and Circumferences of Circles from 1-64 to 4 inches in diameter varying by sixteenths; 
and from 4 incurs to 100 inches varying by one-eighth inch. 



Diam. 


Area 


Circum. 


Diam. 


Area 


Circum. 


Diam. 


Area 


Circum. 


in 


in Square 


in 


in 


in Square 


in 


in 


in Square 


in 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


34-S 


955-25 


IO9.56 


4i.i 


I360.S 


I3O.8 


4 S.| 


1837.9 


'52. 


35 




962.11 


IO9.96 


a 
■1 


I369- 


I3I.2 


# i 


i' s 47-5 


152.4 




JL 
8 


96S.99 


HO.35 


1377-2 


131. 6 


•§ 


1857. 


I52.S 




4 


975-91 


IIO.74 


42- K 


I385.4 


I3I.9 


3 

•4 


1S66.5 


153-2 




3 
8 


982.84 


III 13 


i 


1393-7 


132.3 


7 
•8 


1S76.1 


153-5 




I 


9S9.80 


111-53 


•4 


1402. 


132.7 


49- 


1SS5.7 


153-9 




§ 


996.78 


III. 92 


■s 


1410.3 


133- 1 


j. 


IS95-4 


154-3 




i 

i 


1003.79 


II2.3I 


1 


1418.6 


133-5 


1 
•4 


1905. 


154-7 




ioio.So 


II2./0 


1427. 


133-9 


•§" 


•1914-7 


155-1 


36 




1017.SS 


II3.IO 


a 
•4 


1435-4 


134-3 


1 

.-2 


1924.4 


155-5 




k 


1024.95 


H3-49 


■i 


1443.8 


134-7 


J> 


1934- 1 


155-9 




1 
4 


1032.06 


113.88 


43- 


1452.2 


I35.I 


3 

•8 


1943-9 


156-3 




1 


1039.19 


114.28 


.* 


1460.6 


135-5 


1953-7 


156.7 




£ 


1046.35 


114.67 


•4 


1469. 1 


135-9 


50. 


1963-5 


157-1 




i 


1053-52 


115.06 


•§" 


1477-6 


136.3 


1 


1973-3 


157-4 




a 

i 


1060.73 


H5-45 


1 


1486.2 


156.7 


J. 
•4 


1983.2 


157-9 




1067.95 


115.85 


•f 


1494-7 


I37.I 


•8 


1993- 


15S.2 


37 




1075-2 


116.2 


a 

•i 


I503-3 


137-4 


■* 


2003. 


158.7 




i 


10S2.5 


116.6 


.I5".9 


137-8 


•1 


2012. 8 


159- 




4 


10S9.8 


117. 


44- 


1520.5 


13S.2 


a 
.4 


2022.S 


159-4 




8 


1097 1 


1 17-4 


-i 


1529-2 


133.6 


•8 


2032.8 


i59-8 




h 


1 104-5 


117.8 


i 
•4 


^537-9 


T39- 


51, 


2042. S 


160.2 




8 


iiii.S 


11S.2 


•8 


1546.5 


139-4 


.'* 


2052.8 


160.6 




a 
4 


1119.2 


iiG.6 


.h 


!555-3 


139.8 


1 
.4 


2062.9 


161. 




a. 


1 126.7 


119. 


5 

•8 


1564. 


140.2 


3 

•8 


2072.9 


161.3 


3S 




"34-1 


119.4 


3 
■8 


1572.S 


140.6 


i 


20S3.1 


161. 8 




j. 

8 


1141.6 


119.8 


1581.6 


141. 


•H 


2093.2 


162.1 




4 


1 149. 1 


120.2 


45- 


1590.4 


141.4 


a 

•8 


2103.3 


162.6 




1 


1156.6 


120.6 


•i 


1599-3 


141. s 


2H3-5 


162.9 




i 


1164.2 


121. 


x 
•4 


1608.2 


142.2 


52. 


2123.7 


163.4 




1 


H7I-7 


121. 3 


•8" 


1617. 


142.6 


X 


2133.9 


163.7 




a 

! 

8 


1 1 79-3 


121. 7 


•* 


1626. 


142.9 


.4 


2144.2 


164. 1 




11S6.9 


122.1 


•1 


16349 


143-3 


3 

•8 


2154-4 


164.5 


39 




1 194.6 


122.5 


3 
•8 


I643-9 


143-7 


■k 


2164.S 


164-9 




f 


1202.3 


122.9 


1652.9 


144-1 


■ i 


2175- 


165.3 




4 


1210. 


123-3 


46. 


1661.9 


144-5 


a 

•8 


21S5.4 


165.7 




8 


1217.7 


123.7 


^ 


1671. 


144-9 


2195-7 


166. 1 




| 


1225.4 


1 24. 1 


J. 
■4 


16S0. 


145-3 


53- 


2206.2 


166.5 




i 


1233-2 


124-5 


•8 


16S9.1 


145.7 


i. 

•8 


2216.6 


166.8 




a 
4 


1241. 


124.9 


:| 


1698.2 


146. 1 


X 
•4 


2227. 


167.3 




8 


124S.8 


125-3 


1707.4 


146.5 


•8 


2237.5 


167.6 


40 




1256.6 


125.6 


a 


1716.5 


146.9 


•* 


2248. 


168. 1 




1 


1264.5 


126. 


1725-7 


147.3 


-f 


2258.5 


168.4 




i 


1272.4 


126.4 


47- 


1734.9 


147.7 


a 

.4 


2269. 


16S.9 




8 


1280.3 


126.8 


■i 


1744.2 


148. 


•8 


2279.6 


169.2 




i 


12SS.2 


127.2 


x 


1 753-5 


148.4 


54- 


2290.2 


1696 




■t 


1296.2 


127.6 


•3 


1762.7 


14S.S 


•£ 


2300. S 


170. 




a 
1 


1304-2 


128. 


JL 
■J 


1772.1 


149-2 


J. 
•4 


2311-5 


170.4 




1312.2 


128.4 


h. 


1781.4 


149-6 


3 
•8 


2322.1 


170.8 


41 




1320.3 


12S.8 


'a 


1790.S 


150. 


•i 


2332.S 


171.2 




i 


1328.3 


129.2 


1800.T 


150.4 


5. 

•8 


2343-5 


171.6 




I 

•4 


1336.4 


129.6 


48. 


1809.6 


150.8 


a 

"i 

•8 


2354-3 


172. 




1 


1344.5 


130. 


Jk 


1819. 


151. 2 


2365 


T" 2 ^ 


•* 


1352.7 


130.4 


X 

•4 


182S.5 


151.6 


55. 


2375. 8 


172.8 



292 



Steam Engine Indicator 



Table No. 7. — Continued. 

Areas and Circumferences of Circles from 1-64 to 4 inches in diameter varying by sixteenths; 
and from 4 inches to 100 inches, varying by one-eighth inch. 



Diam. 


Area 


Circum. 


Diam 


Area 


Circum. 


Diam. 


Area 


Circum. 


in 


in Square 


in 


in 


in Square 


in 


in 


in Square 
Inches. 


in 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches; 


55- 4 

i 


2386.6 


173- 1 


6rJ 


3006.9 


194-3 


68.J 


3698.7 


215-5 


2397-5 


173-6 


62. 


3019.I 


1948 


•f 

a 8 


3712.2 


215-9 


2408.3 


173-9 


•4 


3031.2' 


I95-I 


3725.7 


216.3 


•h 


2419.2 


174.4 


1 
•4 


3043-5 


195-6 


69.. 


3739-3 


216.7 


4 


243°- 1 


174.7 


3 

•8 


30557 


195-9 


.4 


3752.8 


217.I 


3 

j 


2441- 


I75-I 


:! 


3068. 


r 96.3 


■4 


3766,4 


217.5 


2452., 


175-5 


30S0.2 


196.7 


3. 


378o. 


217.9 


56. 


2463. 


175-9 


a 


3092.6 


197-r 


•4 


3793-7 


218.3 


1 


■2474. 


176.3 


3104.S 


197-5 


•f 


3S07.3 


218.7 


24S5. 


176.7 


63. 


3117.2 


197-9 


:| 


3821. 


219.I 


3 

•8 


2496. 1 


177.1 


.* 


3129.6 


198.3 


3834-7 


219-5 


•4 


2507.2 


177-5 


.* 


3142. 


198.7 


70. 


3848.5 


219.9 


4 


2518.2 


177.8 


.§ 


3154-4 


199. 


.4 


3862.2 


220.3 


•8 


2529.4 


178.3 


4 


3166.9 


199-5 


•4 


3876. 


220.7 


2540.5 


178.6 


■1 


3 T 79-4 


199.8 


.1 


3S89.8 


221. 


57- 


2551-8 


179. 1 


:i 


3i9 x -9 


200.3 


•:I 


3903.6 


221.5 


•# 


2562.9 


179-4 


3204.4 


200.6 


3917.4 


221.8 


J. 
•4 


2574-2 


179.9 


64. 


3217. 


20I.I 


.1 


3931-4 


222.2 


3 


25S5-4 


180.2 


•f 


32295 


201.4 


.4 


3945-2 


222.6 


•^ 


2596-7 


180.6 


• 4 


3242.2 


20I.8 


n \ 


3959-2 


223. 


•8 


2608. 


iSr. 


3 

•s 


32548 


202.2 


.4 


3973-1 


223.4 


■f 


2619.4 


181.4 




3267.5 


202.6 


.4 


39S7-I 


223.8 


2630.7 


i8r.8 


•1 


3280.1 


203. 


•f 


4001. 1 


224.2 


5& 


2642.1 


182.2 


•f 


^292.8 


203.4 


,4 


4015-2 


224.6 


1 

•8 


2653.4 


1S2.6 


•8 


3305.5 


203.8 


.f 


4029.2 


225. 


•4 


2664.9 


183. 


65. 


3318.3 


204.2 


•f 


4043-3 


225.4 


■# 


2676.3 


rS 3 -3 


•4 


3331- 


204.5 


J 

72. 


4057- 


225.8 


"? 


2687.8 


183.8 


•4 


3343-9 


205. 


4071-5 


226.2 


•1 


2699.3 


1S4.1 


-I 


3356.7 


205.3 


.4 


4085.6 


226.5 


3 

'I 
•8 


2710.9 


184.6 


4 


3369-6 


205.8 


.i 


4099. S 


227. 


2722.4 


184.9 


• I 


3382.4 


206.I 


•f 


4114. 


227.3 


59- 


2734. 


185.4 


a 

1 

• 8 


3395-3 


206.6 


.+ 


4128.2 


227.7 


■4 


2745-5 


185.7 


3408.2 


206.9 


•I 


4142.5 


228.1 


4 


2757-2 


1S6.1 


66. 


3421.2 


207.3 


.£ 


4156.8 


228.5 


•8 


2768.8 


186.5 


•f 


3434- 1 


207.7 


-4 


4171. 


228.9 




2780.5 


186.9 


•4 


3447 2 


208.I 


73- 


4185.4 


229.3 


•1 


2792.2 


187.3 


•8 


346o. 1 


208.5 


.4 


4199.7 


229.7 


a 


2803.9 


187.7 


■4 


3473-2 


208.9 


.i 


42 14. 1 


23O.I 


2815.6 


188. 1 


■1 


3486.3 


209..3 


.1 


4228.5 


230.5 


60. 


2827.4 


188.5 


3 


3499-4 


209.7 


•4 


4242.9 


23O.9 


•4 


2839.2 


188.8 


3512.5 


2IO. 


.# 


42.57-3 


23I.3 


1 
•4 


2851. 


189.3 


67. 


3525-6 


2I0.5 


.f 


4271.8 


23I.7 


•8 


2862.8 


189.6 


.4 


3538.8 


2IO.S 


•4 


4286.3 


232. 


•4 


2874.8 


190. 1 


•4 


3552. 


211. 3 


74- 


4300.8 


232.5 


■i 


28S6.6 


190.4 


a 

•8 


3565-2 


2II.G 

212. 1 


.4 


4315.3 


232.8 


a 


2898.5 


190.9 


•2 


3578.5 


.4 


4329.9 


233.2 


2910.6 


191. 2 




3591-7 


212.4 


.1 


4344-5 


233-6 


61. 


2922.5 


191. 6 


:J 


3605. 


212.8 


.4 


4359-2 


234- 


•4 


2934-4 


192. 


36i33 


213.2 


.4 


4373-8 


234-4 


•4 


2946.5 


192.4 


68. 


363I-7 


213.6 


.f 


4388.5 


234.8 


•8 


2958.5 


192.8 


•f 


3645- 


214. 


•4 


4403.1 


235-2 


''4 


2970.6 


193.2 


4 


3658.4 


2144 


75- 


4417.9 


235-6 


•i 


2982.6 


193.6 


3 

•8 


3671.8 


214.8 


• 4 


4432.6 


236. 


a 
•4 


2994.8 


194. 


•4 


3685.3 


215.2 


•4 


4447.4 


236.4 



And Its Appliances. 



293 



Table No. 7. —Continued. 

Areas and Circumferences of Circles from 1-64 to 4 inches in diameter varying by sixteenths; 
and from 4 inches to 100 inches, varying by one-eighth inch. 



Diam. 


Area 


Cireum. 


Diam. 


Area 


Circum. 


Diam. 


Area 


Circum. 


in 


in Square 


in 


in 


in Square 


in 


Ill 


in Square 


in 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Indies. 


Inches. 


Inches. 


75-1 


4462. 1 


236.7 


S2.1 


5297-1 


258. 


ss.£ 


6203.6 


279.2 


•I 


4477- 


237.2 


1 
•4 


5313-3 


258.4 


89. 


6&X.1 


279.6 


•8 


4491. s 


237-5 


•8 


5329-4 


25S.S 


>ft 


6238.6 


2S0. 


3 

•8 


4506.7 


238. 




5345-6 


259.2 


1 

•4 


6256.1 


2S0.4 


4521-5 


238-3 


■H 


5361.8 


259.6 


•S 


6273.6 


280.8 


76 


4536-5 


23S.8 


2 

•4 


537S.I 


260. 


•* 


6291.2 


281.2 


1 
•H 


4551-4 


239.I 


1 

•8 


5394-3 


260.4 


•8 


630S.8 


2S1.6 


1 
•4 


4566.4 


239-5 


83- 


5410.6 


260.8 


a 

■ 4 


6326.4 


2S2. 


•i 


45Si.3 


239-9 


1 

•8 


5426.9 


261. 1 


1 


6344- 


282.3 


i 


4596-3 


240.3 


1 
•4 


5443-3 


261.5 


90." 


6361.7 


282.7 


•8 


4611.3 


240.7 


•8 


5459-6 


261.9 


1 

•K 


6379-4 


283.I 


3. 


4626.4 


241. 1 


1 


5476. 


262.3 


•4 


6397-1 


283.5 


4641-5 


241-5 * 


5 
•8 


5492.4 


262.7 


•8 


6414.8 


283.9 


77- 8 


4656.6 


241.9 


3 
•4 


550S.S 


263.I 


1 
•2 


6432.6 


2S4.3 


• 1 

•8 


4671-7 


242.2 


7 
•8 


5525-3 


263.5 


•8 


6450.4 


284-7 | 


± 
•4 


46S6.9 


242.7 


84. 


5541-8 


263.9 


:J 


646S.2 


285.I 


3 
•8 


4702. 1 


243- 


X 


555S.3 


264.3 


64S6. 


285-5 


^ 


4717-3 


243-5 


•T 


5574-8 


264.7 


91. 


6503.9 


285.9 


•f 


4732-5 


243-8 


•5 


5591-3" 


265/ 


1 


6521.7 


2S6-3 


•f 


4747-8 


244-3 


.* 


'5607.9 


265.5 


•4' 


6539-7 


2S6.7 


7 
•8 


4765. 


244.6 


•8 


5624-5 


265.8 


3 

•8 


6557.6 


287.I 


7 8 


4778.4 


245- 


3 
•4 


5641.2 


266.2 


^X 


6575-5 


287.5 


.* 


4793-7 


245-4 


7 

•8 


5657.S 


266.6 


•8 


6593-5 


2S7.8 


1 
•4 


4S09. 


245-8 


S5- 


5674-5 


267.. 


•4 


661 1.5 


2S8.2 


•i 


4824.4 


246.2 


•1 


5691.2 


267.4 


1 
•8 


6629.5 


2SS.6 


.* 


4S39.8 


246.6 


•4' 


5707.9 


267.S 


92. 


6647.6 


289. 


•1 


4S55- 2 


247- 


» 


5724.6. 


26S.2 


1 
•8 


6665.7 


2S9.4 


5 
•4 


4S70.8 


247-4 


•2 


574 T -5 


268.6 


1 
•4 


6683.8 


2S9.8 


•8 


4SS6.1 


247-7 


•f 


.575S.2 


26S.9 


•8 


6701.9 


290.2 


79- 


4901 -7 


248. 2 


3 

•4 


5775-1 


269.4 


1 
•2 


6720.1 


290.6 


-4 


4917.2 


248.5 


1 


579^-9 


269.7 


•I 


6738.2 


291. 


■* 


4932.7 


249- 


86*. 


5808. S 


270.2 


3 


6756.4 


291.4 


•8 


4948.3 


249-3 


•8 


.5S25.7 


270.5 


6774.7 


29I.8 


•* 


4963-9 


249-8 


1 
•4 


5S42.6 


271. 


93-, 


6792.9 


292.2 


•1 


4979-5 


250.1 


3 

•8 


5859.5 


271.3 


•f 


6811.1 


292.6 




4995- 2 


250.5 


■* 


5876.5 


271.7 


•4 


6829.5 


293- 


5010.8 


2509 


•1 


5S93-5 


272.I 


■1 


6847.8 


293-4 


80. • 


5026.5 


251-3 


2 

•4 


5910.6 


272.5 


■* 


6866. 1 


293-7 


i 


5042.2 


25i:7 


7 
•8 


5927-6 


272.9 


•8 


6884.5 


294-1 


•4- 


505S. 


252.1 


87. 


5944-7 


273-3 


3 

:i 


6902.9 


294-5 


3 
•8 


5073-7 


252.5 


1 

•8 


5961.7 


273-7 


6921.3 


294.9 


i 


5089.6 


252.9 


i. 
•4 


5978.9 


•274. 1 


94- 


6939.8 


295-3 


-1 


5105.4 


253-3 


•8 


5996. 


274-4 


•f 


6958.2 


295-7 


■I 


5121.2 


253-7 


•* 


6013.2 


274-9 


.4 


6976.7 


296.1 


5I37.I 


254-1 


•1 


6030.4 


275.2 


3 

•8 


6995.2 


296.5 


8l. 


5I53- 


254-5 


:] 


6047.6 


275-7 


1 

•8 


7013.8 


296:9 


• ^ 


5^68.9 


254-9 


6064.8 


276. 


7032.3 


297-3 


•4 


5184.9 


255-3 


88. 


60S2.1 


276.5 


2 

i 

•8 


7051- 


297-7 


•1 


5200.8 


255-6 


•* 


6099.4 


276.8 


7069.5 


298.1 


.A 


5216.8 


256. 


i 


6116.7 


277.2 


95- 


7088.2 


298.5 


•1 


5232.8 


256.4 


i 


6134. 


277.6 


•t 

•4 


7106.9 


298.8 


.4 


5248.9 


256.8 




6151-4 


278. 


7125.6 


299.2 


, ' 8 


5264.9 


257.2 


•1 


6168.8 


278.4 


3 

•8 


7144.3 


299.6 


82. 


5281. 


257.6 


•I 


6186.2 


278.8 


•i 


7163. 


300. 



2 9 4 



Steam Engine Indicator 



Table No. 7.— Continued. 



Areas and Circumferences of Circles from 1-64 to 4 inches in diameter, varying \>y sixteenths; 
and from 4 inches to 100 inches, varying by one-eighth inch. 



Diam. 


Area 


Circum. 


Diam. 


Area 


Circum. 


Diam. 


Area 


Circum. 


in 


in Square 


in 


in 


in Square 


in 


in 


in Square 


in 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


Inches. 


95-1 


7lSl.8 


300:4 


97-f 


7408.8 


305.1 


98-1 


7639-4 


309.8 




7200.6 


300.8 


•4 


7428. 


305-5 


3 

'1 

•8 


76589 


3IO.2 


7219.4. 


301.2 


•1 


7447-. 


305-9 


7678.2 


310.6 


96 


7238.2 


301.6 


■* 


7466.2 


306.3 


99- 


769- 7 


3ii- 


•f 


7257-1 


302. 


•8 


7485-3 


306.7 


'.* 


77I7-I 


3II-4 


•4 


7276. 


302.4 


2 

•4 


7504-5 


307.I 


•4 


7736.6 


311.8 


3 

•8 


7294.9 


302.8 


•* 


752.3-7 


307-5 


3 
•g 


7756.1 


312.2 


-J 


7313.8 


303.2 


98. 


7543- 


307-9 


j 


7775-6 


312.6 


4 


7332.8 


303.5 


■i 


7562.2 


308.3 


•f 


7795-2 


313. 


:1 


7351-8 


3039 


1 
•4 


7581.5 


308.7 


1 : ? 


7814.8 


313 4 


7370.7. 


304-3 


■i 


7600.8 


309. 


7834-3 


313-8 


97. 


'7389.8 


304-7 


.* 


7620. 1 


309-4 


100. 


7854. 


3H-2 



If the areas of larger circles are required, they will be found 
by the following : 

Rule — Multiply the square of the diameter in inches, by 
the decimal 0.7854, and the product will be the area in square 
inches ; or, multiply half the circumference by half the diam- 
eter. If the circumference of a larger circle is wanted, and 
having the diameter, the rule is as follows : 

Rule — As 7 is to 22, so is the diameter to the circumfer- 
ence, or diameter multiplied by 3.i4 l6 equal circumference. 



And Its Appliances. 



295 



Table No. 8. 

The properties of Saturated Steam. 



Pressure per 




Number of British Thermal Units in 


Weight 


Number 


Squa 


re Inch. 




One Pound from Zero (Fahrenheit), 


of One 


of 






Temp- 








Cubic 
Foot of 


Cubic 
Feet of 


Total 


Pressure 


erature in 


Number 


Number of 


Total 


Pressure 


in Pounds 






Units of Heat 


Number 


Steam 


Steam 


iu 


as 


Fahrenheit 


of Units of 


Required for 


of Units of 


in 


from One 


Pounds 


Shown by 


Degrees. 


Heat in 


Evaporation, 
Called 


Heat 


Decimals 


Cubic 


from u 


Steam 






Contained 


of a 


Foot of. 


Vacuum 


Gauge. 




Water. 


Latent Heat. 


in Steam. 


Pound. 


Water. 


L 




102. 


102.086 


1042.964 


1145.050 


.0030 


20620.0 


2 




126.263 


126.440 


1026.010 


1152.450 


.0053 


10720.0 


3 




141.622 


141.877 


1015.254 


1157.131 


.0085 


7326.0 


4 




153.070 


153.396 


1007.229 


1160.625 


.0112 


5600.0 


5 




162.330 


162.722 


1000.727 


1163.449 


.0137 


4535.0 


G 




170.123 


170.577 


995.249 


1165.826. 


.0163 


3814.0 


7 




176.910 


177.425 


990.471 


1167.896 


.0189 
.0214 


3300.0 


•8 




182.910 


183.481 


986.245 


1169.726 


2910.0 


9 




188.316 


188.941 


982.434 


1171.375 


.0239 


2607.0- 


10 




193.240 


193.919 


978.958 


1172.877 


.0264 


2360.0 


11 




197.768 


198.496 


975.762 


1174.258 


.0289 


2157.0 


12 




201.960 


202.737 


972.800 


1175.537 


.n3l3 


1988.0 


13 




205.885 


206.709 


970.025 


1176.734 


.0337 


1846.0 


14 




209.560 


210.428 


967.427 


1177.855 


.0362 


1722.0 


14.7 




212.000 


212.900 


965.700 


1178.600 


.03797 


1644.0 


15 


' ' '.304 


213.025 


213.939 


964.973 


1178.912 


.0:;87 


1612.0 


16 


1.304 


216.296 


217.252 


962.657 


1179.909 


.0413 


1514.0 


17 


2.304 


219.410 


220.409 


960.450 


1180.859 


.0437 


1427.0 


18 


3.304 


222.378 


223.419 


958.345 


1181.764 


.0462 


1350.6 


19 


4.304 


225.203 


226.285 


956.343 


1182.623 


.0487 


1282.1 


20 


5.304 


227.917 


229.039 


954.415 


1183.454 


.0511 


1220.3 


21 


6.304 


230.515 


231.676 


.952.570 


1184.246 


.0536 


1164.4 


22 


7.304 


233.017 


234.218 


950.791 


1185.009 


.0561 


1113.5" 


23 


8.304 


235.432 


236.672 


949.072 


1185.744 


.0585 


1066.9 


24 


9.304 


237.752 


239.029 


947.424 


1186.453 


.0610 


1024.1 


23 


10.304 


240.000 


241.314 


945.825 


1187.139 


.0634 


984.8' 


26 


11.304 


242.175 


243.526 


944.277 


1187.803 


.0658 


948.4 


27 


12.304 


244.284 


241.671 


942.775 


1188.446 


.0683 


914.6 


28 


13.304 


246.326 


247.748 


941.321 


11S9.069 


.0707 


883.2 


29 


14.304 


248.310 


249.769 


939.905 


1189.674 


.0731 


854.0 


30 


15.304 


250.245 


251.738 


938.925 


1190.263 


.0755 


826.'8 


31 


16.304 


252.122 


253.648 


937.1878 


1190.8358 


.0779 


801.2 


32 


17.304 


253.952 


255.512 


935.8818 


1191.3938 


.0803 


777.2/ 


33 


18.304 


255.735 


257.329 


934.60S8 


1191.9378 


.0827 


754.7 


34 


19.304 


257.476 


259.103 


933.3658 


1102.4688 


.0851 


733.5 


35 


20.304 


259.176 


260.835 


932.1523 


1192.9873 


.0S75 


713.4 


36 


21.304 


260.835 


262.527 


930.9608 


1193.4938 


.0^99 


694.5 


37 


22.304 


262.458 


264.182 


929.8068 


1193.9888 


.0922 


676.6 


38 


23.304 


264.045 


265.801 


928.6718 


1194.4728 


.0946 


659.7 


39 


24.304 


265.599 


267.386 


927.5608 


1194.9468 


.0970 


643.6 


40 


25.304 


267.120 


268.938 


926.4728 


1195.4108 


.0994 


628.2 


41 


26.304 


268.611 


270.460 


925.4058 


1195.8658 


.1017 


613.4 


42 


27.304 


270.073 


271.954 


924.3578 


1196.3118 


,1041- 


599.3 


43 


28.304 


271.507 


273.417 


923.3323 


1196.7493 


.1064 


586.1 


44 


29.304 


272.915 


274.855 


922.3238 


1197.1788 


.1088 


573.7 


45 


30.304 


274.296 


276.266 


921.3343 


1197.6003 


.1111 


561.8 


46 


31.304 


275.652 


277.651 


920.3632 


1198.0142 


.1134 


550.4 


47 


32.304 


276.986 


579.016 


919.4052 


1198.4212 


.1158 


539.5 


48 


33.304 


278.297 


280.355 


918.4662 


1198.8212 


.1181 


529.0 


49 


34.304 


279.5S5 


2S1.672 


917.5422 


1199.2142 


.1204 


518.6 


50 


35.304 


280.854 


282.969 


916.6316 


1199.6006 


.1227 


508.5 


51 


36.304 


282.099 


284.243 


915.7377 


1199.9807 


.1251 


499.1 


52 


37,304 


283.326 


285.499 


914.8557 


1200.3547 


.1274 | 


490.1 



296 



Steam Engine Indicator 



Table No. 8.— Continued. 

The Properties of Saturated Steam, 



Pressure per 




Number of British Thermal Units in 


Weight 


Number 


Square Inch. 


Temp- 


One Pound from Zero (Fahrenheit). 


of One 


of 












Cubic 
Foot of 


Cubic 
Feet of 


Total 


Pressure 


erature in 


Number 


Number of 


Total 


Pressure 


in Pounds 






Units of Heat 


Number 


Steam 


Steam 


in 


as 


Fahrenheit 


of Units of 


Required for 


of Units of 


in 


from One 


Pounds 


Shown by 


Degrees. 


Heat in 


Evaporation, 


. Heat 


Decimals 


Cubic 


from a 


Steam 






Called 


Contained 


of a 


Foot of 


Vacuum 


Gauge. 




Water. 


Latent Heat. 


in Steam. 


Pound. 


Water. 


53 


38.304 


284.534 


286.736 


913.9871 


1200.7231 


.1297 


481.4 


'54 


39.304 


285.724 


287.952 


913.1340 


1201.0860 


.1320 


472.9 


55 


40.304 


286.897 
288.052 


289.153 


912.2906 


1201.4436 


.1343 


464.7 


56 


41.304 


290.335 


911.4611 


1201.7961 


.1366 


457.0 


57 


42.304 


289.112 


291.503 


910.6407 


1202.1437 


.1388 


449.6 


58 


43.304 


290.316 


292.654 


909.8325 


1202.4865 


.1411 


442.4 


59 


44.304 


291.425 


293.790 


909.0346 


1202.8246 


.1434 


435.3 


60 


45.304 


292.520 


294.911 


908.2472 


1203.1582 


.1457. 


428.5 


61 


46.304 


293.598 


296.016 


907.4713 


1203.4873 


.14793 


422.0 


62 


47.304 


294.663 


297.108 


906.7042 


1203.8122 


.15021 


415.6 


63 


48.304 


295.714 


298.185 


9U5.9477 


1204.1329 


.15248 


409.4 


64 


49.304 


296.752 


299.249 


905.2005 


1204.4495 


.15471 


403.5 


65 


50.304 


297.777 


300.300 


904.4621 


1204.7621 


.15697 


397.7 


66 


51.304 


298.789 


301.338 


903.7327 


1205.07U7 


.15921 


392 1 


67 


52.304 


299.789 


302.364 


903.0116 


1205.3756 


.16147 


386.6 


68 


53.304 


300.776 


303.377 


902.2999 


120o.6769 


.16372 


381.3 


69 


54.304 


301.753 


304.380 


901.5947 


1205.9747 


.16598 


376.1 


70 


55.304 


302.718 


305.370 


900.8991 


1206.2691 


.16817 


371.2 


71 


56.304 


303.673 


306.350 


900.2101 


1 206.560 L 


.17038 


366.4 


72 


'57.304 


304.617 


307.320 


899.5280 


1200.8480 


. 17259 
.17481 


361.7 


73 


58.304 


305.551 


308.279 


898.8537 


1207.1327 


357.1 


74 


59.304 


306.474 


309.228 


898.1863 


1207.4143 


.17704 


352.6 


75 


60.304 


307.388 


310.166 


897.5209 


1207.6929 


.17923 


348.3 


76 


61.304 


308.290 


311.092 


896.8764 


1207.9684 


.18142 


3441 


77 


62.304 


309.184 


312.011 


896.2301 


1 208.241 1 


.18360 


340.0 


78 


63.304 


310.069 


312.920 


895.5910 


1208.5110 


.18579 


336.0 


79 


64.304 


310.945- 


313.821 


894.9571 


1 208.778 L 


.18797 


332.1 


80 


65.304 


311.812 


314.712 


894.3304 


1209.0424 


.19015 


328.3 


81 


66.304 


312.670 


315.595 


893.7092 


lL'09.3042 


.19232 


324.6 


82 


67.304 


313.520 


316.468 


893.0954 


1209.5634 


.19454 


320.9 


83 


68.304 


314.361 


317.333 


892.4871 


1209.8201 


.19674 


317.3 


84 


69.304 


315.195 


318.190 


891.8843 


1210.0743 


.19887 


313.9 


85 


70.304 


316.021 


319.040 


891.2862 


.1210.3262 


.20105 


310.5 


86 


71.304 


316.839 


319.882 


890.6938 


1210.5758 


.20321 


307.2 


87 


72 304 


317.650 


320.717 


890.1061 


1210.8231 


.20535 


304.0 


88 


73.304 


318.453 


321.543 


889.5251 


1211.0681 


.20753 


300.8 


89 


74.304 


319.249 


322.362 


888.94f)0 


1211.3110 


.20970 


297.7 


90 


75.304 


320.039 


323.176 


888.3758 


1211.5513 


.21183 


294.7 


91 


76.304 


320.82 L 


323.981 


887.8094 


1211.7904 


.21393 


291.8 


92 


77.304 


321.597 


324.781 


887.2460 


1212.0270 


.21608 


288.9 


93 


78.304 


322.366 


325.572 


886.6896 


1212.2616 


.21829 


280.1- 


94- 


79.304 


323.128 


326.358 


886.1362 


1212.4942 


.2204"> 


283.3 


95 


80.304 


323.884 


327.136 


885.5887 


1212.-7247 


.22247 


280.6 


96 


81.304 


324.634 


327.909 


885.0444 


1212.9534 


.22455 


278.0 


97 


82.304 


325.378 


328.675 


884.5052 


1213.1802 


.22067 


275.4 


98 


83.304 


326.114 


329.433 


883.9721' 


1213.4051 


.22883 


272.8 


99 


84.304 


326.845 


330.186 


883.4421 


1213.6281 


.23095 


270.3 


100 


85.304 


327.571 


330.935 


882.9144 


1213.8494 


.23302 


267.9 


101 


86.304 


328.291 


331.678 


882.3909 


1214.U689 


.23510 


265.5 


102 


87.304 


329.005 


332.414 


881.8727 


1214.2807 


.23717 


263.2 


103 


88.304 


329.714 


333.145 


881.3577 


1214.5027 


.23925 


260.9 


104 


89.304 


330,416 


333.869 


880.8481 


1214.7171 


.24132 


258.7 


105 


90.304 


331.113 


,334.587 


880.3429 


1214.9299 


.24340 


256.5 



/Lnd Its Applia 



nces. 



297 



Table No. 8.— Continued. 

The Properties of Saturated Steam. 



Pressure per 




Number of 


British Thermal Units in 


Weight 


Number 


Square Inch. 




One Pound from Zero (Fahrenheit). 


of One 


of.. v 






Temp- 








Cubic 


Cubic 


Total 


Pressure 


erature in 


Number 


Number of 1 


Total 


Foot of 


Feet of 


Pressure 


in Pounds 






Units of Heat 


Number 


Steam 


Steam 


in 


as 


Fahrenheit 


of Units of 


Required for 


of Units of 


in 


from One 


Pounds 


Shown by 


Degrees. 


Heat in 


Evaporation, 


Heat 


Decimals 


Cubic 


from u 


Steam 






Called 


Contained 


of a 


Foot of 


Vacuum 


Gauge. 




Water. 


Latent Heat. 


in Steam. 


Pound. 


Water. 


106 


91.304 


331.805 


335.301 


879.8400 


1215.1410 


.24547 


254.3 


107 


92.304 


332.492 


336.009 


879.3416 


-1215.3506 


.24754 


252.2 


103 


93.304 


333.174 


336.714 


878.8447 


1215.5587 


.24961 


250.1 


109 


94.304 


333.85 L 


337.411 


878.3542 


1215.7652 


.25168 


248.0 


110 


95.304 


334.523 


338.105 


877.8653 


1215.9703 


.25376 


246.0 


111 


96.304 


335.19L 


338.795 


877.3789 


1216.1739 


.25582 


244.0 


112 


97.304 


335.854 


339.479 


876.8970 


1216.3760 


.257S8 


242.0 


113 


98.304 


336.511 


340.157 


876.4198 


1216.5768 


.25994 


240.1 


114 


99.304 


337 165 


340.832 


875.9442 


1216.7762 


.26199 


238.2 


115 


100.304 


337.814 


341.502 


875.4721 


1216.9741 


.26405 


236.3 


116 


101.304 


338.459 


342.169 


875.0018 


1217.1708 


.26611 


234.5 


117 


102.304 


339.100 


342.83 L 


874.5352 


1217.3662 


.26816 


232.7 


118 


103.304 


339.736 


343/488 


874.0722 


1217.5602 


.27020 


231.0 


119 


104.304 


340.308 


344.141 


.873.0120 


1217.7530 


.27224 


229.3 


120 


105.304 


34u.yyd 


o44.789 


873.1555 


1217.9445 


.27428 


227.6 


121 


106.304 


341.618 


345.432 


872.7027 


1218.1347 


.27028 


226.0 


122 


107.304 


342.238 


346.073 


872.2508 


1218.3238 


.27828 


224.4 


123 


108.304 


342.854 


346.709 


871.8027 


1218.5117 


.28027 


222.8 


124 


109.304 


343.466 


347.343 


871.3553 


1218.6983 


.28227 


221.2 


125 


110.304 


344.074 


347.972 


870.9118 


12l8.b838 


.28426 


219.7 


126 


111.304 


344.678 


348.596 


870.4721 


1219.0681 


.28625 


218.2 


127 


112.304 


345.279 


349.217 


870.0342 


1219.2512 


.28824 


216.7 


128 


113.304 


345.876 


349.835 


869.5983 


1219.4333 


.29023 


215.2 


129 


114.304 


346.459 


350.448 


869.1663 


1219.6143 


.29222 


213.7 


130 


115.304 


347.059 


351.059 


' 868.7351 


1219.7941 


.29420 


212.3 


131 


1.16.304 


347.644 


351.665 


868.3079- 


1219.9729 


.29618 


210.9 


132 


117.304 


348.22:7 


352.267 


867.8836 


1220.1506 


.29816 


209.5 


133 


118.304 


348.806 


352.867 


807.4601 


1220.3271 


.30013 


208.1 


134 


119.304 


349.382 


353.463 


867.0397 


1220.5027 


.30209 


206.7 


• 135 


120.304 


349.954 


354.055 


866.6223 


1220.6773 


.30405 


205.4 


136 


121.304 


350.523 


354.644 


866.2068 


1220.8508 


.30601 


204.1 


137 


122.304 


351.089 


355.230 


866.7934 


1221.0234 


.30796 


202.8 


138 


123.304 


351.752 


355.813 


865.3820 


1221.1950 


.30990 


201.5 


139 


124.304 


352.211 


356.392 


864.9735 


1221.3655 


.31186 


200.2 


140 


125.304 


352.767 


356.969 


864.5661 


1221.5351 


.31386 


199.0 


141 


126.304 


353.319 


357.541 


864.1627 


1221.7037 


.31587 


197.8 


142 


127.304 


353.869 


358.110 


863.7613 


1221.8713 


.31788 


196.6 


143 


128.304 


354.416 


358.677 


863.3611 


1222.0381 


.31990 


195.4 


144 


129.304 


354.960 


359.240 


862.9640 


1222.2040 


.32190 


194.2 


145 


130.304 


355.501 


359.801 


862.5679 


1222.3689 


.32391 


193.0 


146 


131.304 


356.039 


360.359 


862.1740 


1222.5330 


.32592 


191.9 


147 


132.304 


356.574 


360.913 


861.7832 


1222.6962 


.32794 


190.8 


148 


133.304 


357.106 


361.465 


861.3934 


1222.8584 


.32995 


189.7 


149 


134.304 


857.635 


362.013 


861.O068 


1223.0198 


.33196 


188.6 


150 


135.304 


358.161 


3H2.559 


860.6213 


1223.1803 


.33400 


187.5 


151 


136.304 


358.683 


363.100 


860.2399 


1223.3399 


.33580 


186.4 


152 


137.304 


359.203 


363.640 


859.8588 


1223.4988 


.33761 


185.3 


153 


138.304 


359.721 


364.177 


859.4799 


1223.6569 


.33942 


184.3 


154 


139.304 


360.236 


364.711 


859.1031 


1223.8141 


.34123 


183.3 


155 


140.304 


360.749 


365.243 


858.7276 


1223.9706 


..34304 


182.3 


156 


141.304 


361.260 


365.773 


858.3533 


1224.1263 


.34485 


181.3 


157 


142.304 


361.768 


366.300 


857.9811' 


1224.281 L 


.34666 


1S0.3 


158 


143.304 


362.273 


366.824 


857.6112 


1224.4352 


.34847 


170.3 



Steam Engine 



Indicator 



Table No. 8.— Continued. 

The Properties of Saturated Steam. 



Pressure per 




Number of 


British Thermal Units in 


Weight 


Number 


Square Inch. 


Temp- 


One Pound from Zero (Fahrenheit). 


of One 


of • 












Cubic 
Foot of 


Cubic 
Feet of 


Total 


Pressure 


erature in 


Number 


Number of 


Total 


Pressure 


in Pounds 






Units of Heat 


Number 


Steam 


Steam 


in 


as 


Fahrenheit 


of Units of 


Required for 


of Units of 


in 


from One 


Pounds 


Shown by 


Degrees. 


Heat in 


Evaporation, 
Called 


Heat 


Decimals 


Cubic 


from a 


Steam 






Contained 


of a 


Foot of 


Vacuum 


Gauge. 




Water. 


Latent Heat. 


in Steam. 


Pound. 


Water. 


159 


144:304 


362.776 


367.347 


857.2415 


1224.5885 


.35028 


178.3 


160 


145.304 


363.277 


367.867 


856.8740 


1224.7410 


.35209 


177.3 


1G1 


146.304 


363.774 


368.383 


856.5099 


1224.8929 


.35397 


176.4 


162 


147.304 


364.270 


368.898 


856.1461 


1225.0441 


.35585 


175.5 


163 


148.304 


364.764 


369.410 


855.7846 


1225.1946 


.35773 


174.6 


164 


149.304 


365.255 


369.920 


855.4243 


1225.3443 


.35961 


173.7 


165 


150.304 


365.744 


370.428 


855.0654 


1225.4934 


.36149 


172.8 


166 


151.304 


366.232 


370.934 


854.7077 


1225.6417 


.36337 


171.9 


167 


152.304 


366.717 


371.438 


854.3514 


1225.7894 


.36525 


171.0 


163 


1.53.304 


367.199 


371.939 


853.9974 


1225.9364 


.36714 


170.1 


169 


154.304 


367.680 


372.437 


853.6456 


1226.0826 


.36903 


169.2 


170 


155.304 


368.158 


372.934 


853.2942 


1226.2282 


.37092 


168.4 


171 


156 304 


368.632 


373.427 


852.9461 


1226.3731 


.37272 


167.6 


172 


157.304 


369.105 


373.918 


852.5995 


1226.5175 


.37452 


166.8 


17.3 


15S.304 


369.576 


374.408 


852.2533 


1226.6613 


.37632 


166.0 


174 


159.304 


370.045 


374.895 


851.9094 


1226.8044 


.37812 


165.2 


17) 


160.304 


370.512 


375.380 


851.5670 


1226.9470 


.37992 


164.4 


176 


161.304 


370.978 


375.865 


851.2239 


1227.0889 


.38172 


163.6 


177 


162.304 


371.442 


376.347 


850.8833 


1227.2303 


.38353 


162.8 


178 


163.304 


371.904 


376.827 


850.5441 


1227.3711 


.38534 


162.0 


179 


164.304 


372.364 


377.305 


850.2062 


1227.5112 


.38715 


161.2 


180 


165.304 


372.822 


377.781 


849.8698 


1227.6508 


.38895 


160.4 


181 


1(56.304 


373.275 


378.255 


849.5347 


1227.7897 


.39077 


159.7 


182 


167.304 


373.731 


378.727 


849.201 1 


1227.9281 


.39259 


159.0 


183 


168.304 


374.183 


379.197 


848.8689 


122&0659 


.39441 


158.3 


184 


169 304 


374.633 


379.665 


848.5380 


1228.2030 


.39624 


157.6 


185 


170.304 


375.081 


380.131 


848.2086 


1228.3396 


.39807 


156.9. 


186 


171.304 


375.527 


380.595 


847.8805 


1228.4755 


.39990 


156.2 


187 


172 304 


375.971 


381.056 


847.5549 


1228.6109 


.40173 


155.5 


188 


173.304 


376.413 


381.516 


847.2297 


1228.7457 


.40356 


154.8 


189 


174.304 


376.853 


381.974 


846.9058 


1228.8798 


.40539 


154.1 


190 


175.304 


377.291 


382.429 


846.5844 


1229.0134 


.40722 


153.4 


191 


176.304 


377.727 


382.883 


846.2633 


1229.1463 


.40S99 


152.7 


192 


177.304 


378.161 


383.335 


845.9437 * 


1229.2787 


.41076 


152.0 


193 


178.304 


378.593 


383.785 


845.6256 


1229.4106 


.41253 


151.3 


194 


179.304 


379.023 


384.233 


845.3089 


1229.5419 


.41430 


150.7 


195 


180.304 


379.452 


384.679 


844.9938 


1229.6728 


.41607 


150.1 


196 


181.304 


379.979 


385.123 


844.6801 


1229.8031 


.41784 


149.5 


197 


182.304 


380.305 


385.567 


844.3660 


1 229.9330 


.41962 


148.9' 


198 


183.304 


380.729 


386.003 


844.0543 


1230.0623 


.42140 


148J 


199 


184.304 


381.152 


386.449 


843.7422 


1230.1912 


.42318 


147.7 


200 


185.304 


381.573 


386.887 


843.4326 


1230 3196 


.42496 


147.1 


201 


186.304 


381.992 


387.324 


843.1234 


1230.4474 


.42667 


146.5 


202 


187.304 


382.410 


387.760 


842.8148 


1230.5748 


.42838 


145.9 


203 


188.304 


382.827 


388.194 


842.5076 


1230.7016 


.43009 


145.3 


204 


1 Si). 304 


383.242 


3S8.027 


842.2010 


1230.8280 


.43180 


144.7 


: 205 


190.304 


383.655 


389.057 


841.8969 


1230.9539 


.43351 


144.1 


206 


191.304 


384 066 


389.485 


841.5942 


1231.0792 


.43523 


143.5 


207 


102.304 


384.475 


389.912 


841.2921 


1231.2041 


.43695 


142.9 


208 


103.304 


384.883 


390.337 


840.9914 


1231.3284 


.43866 


142.3 


20!) 


104.304 


385.288 


390.759 


840.6933 


1231.4523 


.44039 


141.8 


210 


195.304 


385.671 


391.179 


840.3967 


1231.5757 


.44211 


141.3 



And its Appliances. 



2 99 



Table No. 9. 

The Properties cf Water from 32 to 212 Fahrenheit. 



. 






Number of Bkitish Thei 


mai. Units in 


Weight 


Number 


Bl.ASTIC rujn-1.. 


Tem- 


One Pound from Zero ( 


Fahrenheit). 


of One 


of 






perature 








Cubic 
Foot of 


Cubic 
Feet of 


Ill Pounds 




Number 


Numbcrof 


Total 




In Inches 


in Fah- 




Units of Heat 


Number 


Vapor 


Steam 


on the 


of 


renheit 


of Units of 


Required for 


of Units of 


in 


from One 


Square 


Heat in 


Evaporation, 


Heat 


Decimals 


Cubic 


Mercury. 


Degrees. 




Called 


Contained 


of a • 


Foot of 


Inch. 






■\Yater. 


Latent Heat. 


in Vapor. 


Pound. 


Water. 


.089 


.1 SI 1 


32 


32.000 


1091.700 


1123.700 


.00030 


208,080 


.092 


.1884 


33 


33.000 


1091.005 


1124.005 


.00030 


200,480 


.096 


.1930 


34 


34.000 


.1090.310 


1124.310 


.00031 


193,180 


.100 


.2039 


35 


35.000 


1089.615 


1124.615 


:00032 


186,180 


.101 


.2121 


36 


36.000 


1088.920 


1124.920 


.00033 


179,380 


.108 


.2205 


37 


37.000 


1088.225 


1125.225 


.00034 


172,780 


.112 


.2292 


38 


38.000 


1087.530 


1125.530 


.00036 


166,380 


.117 


.23S2 


39 


39.001 


10S6.834 


1125.835 


.C0038 


160,230 


.122 


.2476 


40 


40.001 


10S0.139 


1120.140 


.00040 


154.330 


.127 


.2573 


41 


41.001 


1085.444 


1126.445 


.00042 


148,620 


.132 


.2673 


42 


42.001 


1084.749 


1126.750 


.00013 


143,220 


.137 


.2777 


43 


43.001 


1084.054 


1127.055 


.00045 


138,070 


.142 


.2SS4 


44 


44.002 


1083.358 


1127.360 


.00047 


133,120 


.147 


.2994 


45 


45.002 


1082.663 


1127.665 


.00049 


128,370 


.152 


.3109 


46 


46.002 


1081.963 


1127.970 


.CC050 


123,840 


.158 


.3228 


47 


47.002 


1031.273 


1128.275' 


XC352 


119,610 


.164 


.3351 


48 


48.C03 


1080.577 


1128.580 


.C0054 


115,490 


.170 


.3478 


49 


49.C03 


1079.882 


1128.885 


.60053 


111,470 


.176 


.3608 


50 


50.003 


1079.187 


1129.190 


.03053 


107,630 


.183 


.3743 


5L 


51.004 


1078.491 


1 129.495 


.00030 


103,930 


!l90 


.3S83 


52 


52.004 


1077.796 


1129.800 


.00032 


100,330 


.197 


.4028 


53 


53.005 


1077.100 


1130.105 


.60335 


96,930 


.205 


.4177 


54 


54.005 


1076.405 


1130.410 


.00067 


93,680 


.212 


.4332 


55 


55.006 


1075.709 


1130.715 


.00063 


90,540 


.220 


.4492 


56 


56.006 


1075.014 


1131.020 


.00071 


87,500 


.228 


.4656 


57 


57.007 


1074.318 


1131.325 


.00073 


84,560 


.236 


.4825 


58 


58.007 


1073.623 


1131.630 


.00076 


81,740 


.243 


.5000 


59 


59.008 


1072.927 


1131.935 


.00079' 


79,020 


.254 


.5180 


60 


60.009 


1072.231 


1 132.240 


.00082 


76,370 


.263 


.5367 


61 


61.010 


1071.535 


1132.545 


.C00S5 


73,810 


.273 


.5560 


62 


62.011 


1070.839 


1132.850 


.00083 


71,330 


.282 


.5758 


63 


63.012 


1070.143 


1133.155 


.00091 


68,940 


.292 


.5962 


64 


61.013 


1069.417 


1133.460 


.00094 


06,630 


.302 


.6173 


65 


65.014 


1068.751 


1133.785 


.00097 


64,420 


.31*3 


.6391 


66 


66.015 


1068.055 


] 134.070 


.00103 


02,290 


.324 


.6615 


67 


67.010 


1037.359 


1134.375 


.00103 


60.2S0 


.335 


.6846 


68 


68.018 


1066.662 


1134.680 


.00107 


58,340 


.347 


.7084 


69 


69.019 


1065.966 


1134.985 


.00111 


50,470 


.359 


.7330 


70 


70.020 


1085.270 


1135.290 


.00115 


54,660 


.372 


.7583 


71 


71.021 


1064.574 


1135.595 


-.00119 


52,910 




.7844 


72 


72.023 


1063.877 


1135.900 


.00123 


51,210 


'.393 


.8114 


73 


7:5.024 


1063.181 


1136.205 


.00127 


49,570 


.-111 


,8391 


74 


74.026 


1062.484 


1136.510 


.00131 


48,000 


.425 


.8<>76 


75 


75.027 


1061.788 


1136.815 


.00135 


46,510 


.440 


f .«969 


7<j 


76.029 


1061.091 


1137.120 


.00139 


45,060 


.455 


.9271 


77 


77.030 


1060.395 


1137.425 


.00143 


43,650 


.470 


.''.".S3 


78 


78.032 


1059.698 


1137.730 


.00148 


42,280 


.4S6 


.9905 


79 


79.034 


1059.001 


1138.035 


.00153 


40,960 


.502 


1 .023 


80 


80.036 


1058.304 


1 1 38.340 


.00158 


39,690 


.518 


1.056 


81 


81.037 


1057.008 


1138.645 


.00163 


38,480 


.535 


i.ooi 


82 


S2.U39 


1056.<)11 


1138.950 


.00163 1 


37,320 



30O. 



Steam Ejigine Indicator 



Table No. 9.— Continued. 

The Properties of Water from 32 to 212 Fahrenheit. 



Elastic 


Force. 




Number of 


British Thermal Units in 


Weight 


Number 


Tem- 


One Pound from Zero (I 


"AHRENHEIT). 


of One 
Cubic 
Foot of 


of 

Cubic 
Feet of 


In Pounds 




perature 


Number 


Number of 


Total 




In Inches 


in Fah- 




Units of Heat 


Number 


Vapor 


Steam 


on the 


of 


renheit 


of Units of 


Required for 


of Units of 


in 


from 0,n e 


Square 


Keat in 


Evaporation) 


Heat 


Decimals 


cubic 




Mercury. 


Degrees. 




Called 


Contained 


of a 


Foot ol 


Inch. 






Water. 


Latent Heat. 


in Vapor. 


Pound. 


W ater. 


.553 


1.127 


83 


83.041 


1056.214 


1139.255 


.00173 


36, mo 


.571 


1.103 


84 


84.043 


1055.517 


1139.560 


.00178 


35,100 


.590 


1.201 


85 


85.045 


1054.820 


1139.865 


.00183 


34,050 


.609 


1:240 


86 


86.047 


1054.123 


1140.170 


.00189 


33,030 


.629 


1.281 


87 


87.049 


1053.428 


1140.475 


.00195 


32,050 


,650 


1.323 


88 


8S.051 


1052.729 


1140.780 


-.00201 


31,100 


.671 


1.366 


89 


89.053 


1052.C32 


1141.085 


.00207 


30,180 


.692 


1.410 


90 


90.055 


1051.335 


1141.390 


.00213 


29,290 


.715 


1.454 


91 


91.057 


1050.638 


1141.695 


.00219 


28,430 


.738 


1.500 


92 


92.059 


1049.941 


1142.000 


.00226 


27,600 


.761 


1.548 


93 


93.061 


1049.244 


1142.305 


.00233 


26,800 


.785 


1.597 


94 


94.063 


1048.547 


1142.610 . 


.00240 


26,020 


.809 


1.647 


95 


95.065 


1047.850 


1142.915 


.00247 


25,270 


.834 


1.693 


96 


96.0C8 


1047.152 


1143.220 


.00254 


24,540 


.860 


1.751 


97 


97.071 


1046.454 


1143.525 


.00262 


23,830 


.8S7 


1.805 


98 


98.074 


1045.756 


1143.830 


.00270 


23,140 


.914 


1.861 


99 


99.077 


1045.058 


1144.135 


.00278 


22,470 


.943 


1.918 


100 


100.080 


1044.360 


1144.440 


.002S6 


21,830 


.972 


1.977 


101 


101.0S3 


1043.662 


1144.745 


.00294 


21,210 


1.001 


2.037 


102 


102.0S6 


1042.904 


1145.050 


.00302 


20,620 


1.031 


2.099 


103 


103.0S9 


1042.206 


1145.355 


.00311 


20,050 


1.062 


2.163 


104 


104.092 


1041.568 


1145.660 


.00320 


19,500 


1.094 


2.227 


105 


105.095 


1040.870 


1145.965 


.00330 


18,970 


1.126 


2^293 


1C6 


106.098 


1040.172 


1146.270 


.00340 


18,460 


1.159 


2.361 


107 


107.101 


1039.474 


1143.575 


.00350 


17,960 


1.193 


2.431 


108 


103.104 


1038.776 


1143.8S0 


.00360 


17,470 


1.229 


2.503 


109 


109.107 


1038.078 


1147.185 


.00370 


16,990 


1.265 


2.577 


110 


110.110 


1037.3S0 


1147.490 


.00380 


16,520 


1.302 


2.653 


111 


111.113 


1036.682 


1147.795 


.00390 


16,070 


1.341 


2.731 


112 


112.117 


1035.983 


1143.100 


.00400 


15,640 


1.381 


2.810 


113 


113.121 


1035.284 


1143.405 


.00410 


15,220 


1.421 


2.892 


114 


114.125 


1034.585 


1148.710 


.00421 


14,820 


1.462 


2.976 


115 


115.129 


1033.886 


1149.015 


.00433 


14,430 


1.504 


3.061 


116* 


116.133 


1033.187 


1149.320 


.00445 


14,050 


1.547 


3.149 


117 


117.137 


1032.4S8 


1149.625 


.00457 


13,680 


1.591 


3.239 


113 


118.141 


1031.789 


1149.930 


.00470 


13,320 


1.636 


3.331 


119 


119.145 


1031.090 


1150.235 


.00483 


12.970 


1.682 


3.425 


120 


120.149 


1030.391 


1150.540 


.00496 


12,630 


1.730 


3.522 


121 


121.153 


1029.692 


1150.845 


.00508 


12,300 


1.779 


3.621 


122 


122.157 


1028.993 


1151.150 


.00521 


11,980 


1.828 


3.723 


123 


123.161 


1028.294- 


1151.455 


.00535 


11,670 


1.879 


3.826 


124 


124.165 


1027.595 


1151.760 


.00549 


11,370 


1.931 


3.933 


125 


125.169 


1026.896 


1152.065 


.00563 


11,080 


1.984 


4.042 


126 


126.173 


1026.197 


1152.370 


.00578 


10,800 


2.039 


. 4.153 


127 


127.177 


1025.498 


1152.675 


.00593 


10,530 


2.096 


4.267 


128 


12S.1S2 


1024.798 


1152.980 


.00603 


10,265 


2.154 


4.384 


129 


129.187 


1024.098 


1153.285 


.0082-t 


10,010 


2.213 


4.503 


130 


130.192 


1023.398 


1153.590 


.00640 


9,760' 


2.273 


4.625 


131 


131.197 


1022.698 


1153.895 


.00056 


9,516 


2.335 


4.750 


132 


132.202 


1021.993 


1154.200 


.00673 


9,276 


2.398 

rJBK. 


4.878 


133 


133.207 


•1021.298 


1154.505 


.00690 


9,046 



And its Appliances 



301 



Table No 9. — Continued. 

The Properties of Water from 32 to 212 Fahrenheit. 









Number of British Thermal Units in 


Weieht 


■ «4 

Number 


Elastic run^c. 


Tem- 


One Pou> 


d from Zero (Fahrenheit). 


oi One 


of 






perature 








Cubic 
Foot of 


Cubic 
Feet of 


In Pounds 




Number 


Number of 


Total 




In Inches 


in Fah- 




United Heat 


Number 


Vapor 


Steam 


on the 


of 


renheit 


of Units of 


Required tor 


.of Units of 


in 


from One 


Square 


Heat in 


Evaporation, 


Heat 


Decimals 


Cubic 


Mercury. 


Degrees. 




Called 


Contained 


of a 


Footof 


Inch. 






Water 


Latent Heat, 


in Vapor. 


Pound. 


V\ ater. 


2.461 


5.009 


134 


134.212 


1020.598 


1154.810 


.00707 


8,826 


2.526 


5.143 


135 


135.217 


1019.898 . 


1155.115 


.00725 


8,611 


2.594 


5.280 


136 


136.222 


1019.198 


1155.420 


.00743 


8,401 


2.663 


5.420 


137 


137.227 


1018.498 


1155.725 


.00761 


- 8,191 


2.732 


5.563 


138 


138.223 


1017.797 


1156.030 


,00780 


7,991 


2.803 


5.709 


139 


139.239 


1017.096 


1156.335 


.00799 


7,798 


2.876 


5.858 


140 


140.245 


KH6.395 


1156.640 


.00819 


7.613 


2.952 


6.011 


141 


141.251 


1015.694 


1156.945 


.00839 


7,433 


3.029 


6.167 


142 


142.257 


1014.993 


1157.250 


.00860 


7,258 


3.108 


6.327 


143 


143.263 


1014.292 


1157.555 


.00881 


7,088 


■ 3.188 


6.490 


144 


144.269 


1013.591 


1157.860 


.00903 


6,920 


3.270 


6.657 


145 


145.275 


1012.890 


1158.165 


.00925 


6,755 


3.353 


6.827 


146 


146.281 


1012.189 


1158.470 


.00948 


6,595 


3.438 


7.001 


147 


147.287 


1011.488 


1158.775 


.00971 


6,440 


3.526 


7.179 


148 


148.293 


1010.787 


1159.080 


.00993 


6,290 


3.615 


7.361 


149 


149.299 


1010.086 


1159.385 


.01016 


6,144 


3.707 


7.547 


150 


150.305 


1009.385 


1159.690 


.01040 


6,004 


3.801 


7.736 


151 


151.311 


1008.684 


1159.995 


.01064 


5,867 


3.896 


7.929 


152 


152.318 


1007.982 


1160.300 


.01089 


5,734 


3.992 


8.127 


153 


153.325 


1007.280 


1160.605 


.01114 


5,604 


4.090 


8.329 


154 


154.332 


1006.578 


1160.910 


.01140 


5,477 


4.191 


8.535 


155 


155.339 


1005.876 


1161.215 


.01167 


5,353 


4.295 


8.745 


156 


156.346 


1005.174 


1161.520 


.01194 


5,232 


4.400 


8.959 


157 


157.353 


1004.472 


1161.825 


.01222 


5,114 


4.507 


9.178 


158 


158.360 


1003.770 


1162.130 


.01250 


5,000 


4.617 


9.401 


159 


159.367 


1003.068 


1162.435 


.01279 


4,888 


4.729 


9.629 


160 


160.374 


1002.366 


1162.740 


.01308 


4,779 


4.843 


9.861 


161 


161.331 


1001.664 


1163.045 


. .01338 


4,673 


4.980 


10.098 


162 


162.389 


1000.961 


1163.350 


.01363 


4,569 


5.079 


10.340 


163 


163.397 


1000.258 


1163.655 


.01399 


4,467 


5.200 


10.588 


164 


164.405 


999.555 


1163.960 


.01-130 


4,368 


5.324 


10.840 


165 


165.413 


998.852 


1164.265 


.01462 


4,271 


5 451 


11.097 


166 


166.421 


998.149 


1164.570 


.01495 


4,177 


5.530 


11.359 


167 


167.429 


997.446 


1164.875 


.01528 


4,085 


5.711 


11.627 


168 


168.437 


996.743 


1165.180 


.01562 


3,996 


5.845 


11.900 


169 


169.445 


996.040 


1165.485 


.01596 


3,910 


5.9S1 


12.178 


170 


170.453 


995.337 


1165.790 


.01631 


3,826 


6.120 


12.461 


171 


171.461 


994.634 


1166.095 


.01667 


3,744 


6.262 


12 750 


172 


172.470 


993.930 


1166.400 


.01704 


3,664 


6.408 


13.045 


173 


173.479 


993.226 


1166.705 


.01741 


3,586 


6.555 


13.345 


174 


174.488 


992.522 


1167.010 ' 


..01779 


3,510 


6.704 


13.651 


175 


175.497 


991.818 


1167.315 


.01817 


3,436 


6.857 


13.963 


176 


176.506 


991.114 


1167.620 


.01855 


3,365 


7.013 


14.2S1 


177 


177.515 


990.410 


1167.925 


.01894 


3,295 


7.172 


14.605 


178 


178.524 


989.706 


1 168.230 


.01934 


3,226 


7.335 


14.935 


179 


179.533 


989.002 


1168.535 


.01975 


3,159 


7.500 


15.271 


ISO 


180.542 


988.298 


' 1168.840 


.02017 


3,093 


7.668 


15.614 


181 


181.551 


987.594 


1169.145 


.02060 


3,029 


7.841 


15.963 


182 


182.561 


986.889 


1169.450 


.02104 


2,966 


8.016 


16.318 


183 


183.571 


986.184 


'1169.755 


.02148 


2,905 


8.194 


16.6S0 


1S4 


184.581 


985.479 


1170.060 


.02193 


2,846 



;02 



Steam Engine Indicator 



Table No. 9. — Continued. 

The Properties of Water from 32 to 212 Fahrenheit. 



"Rt A CTTr* f?r\T*r*T? 




Number of 


British Thermal Units in 


Weight 


Number 


IjLAoXIVj 




Tem- 


One Pound from Zero (Fahrenh 


of One 


■of 






perature 








Cubic 
Foot of 


Cubic 
Feet of 


In Pounds 




Number 


Number of 


Total 


x^" 


In Inches 


in Fah- 


of Units of 


Units of Heat 


Number 


Vapor 


Steam 


on the 


of 


renheit 


Required for 


of Units of 


in 


from One 


Square 




Heat in 


Evaporation, 
Called 


Heat 


Decimals 


Cubic 


Mercury. 


Degrees. 




Contained 


of a 


Foot of 


Inch. 






Water. 


Latent Heat. 


in Vapor. 


Pound. 


Water. 


8.375 


17.049 


• 185 


185.591 


984.774 


1170.365 


.02238 


2.789 


8.558 


17.425 


186 


186.601 


984.089 


1170.670 


.02284 


2,733 


8.745 


17.807 


187 


187.611 


983.364 


1170.975 


.02331 


2,678 


• 8.936 


18.196 


188 


188.621 


982.659 


1171.280 


.02379 


2,624 


9.132 


• 18.593 


189 


189.632 


981.953 


1171.585 


.02428 


2,571 


9.330 


18.997 


190 


190.643 


981.247 


1171.890 


.02470 


2,519 


9.532 


19.408 


191 


191.654 


980.541 


1172.195 


.02529 


2,469 


9.738 


19.827 


192 


192.665 


979.835 


1172.500 


.02580 


2,420 


9.947 


20.253 


193 


193.676 


979.129 


1172.805 


.02632 


2,372 


10.160 


20.687 


194 


194.686 


978.424 


1173.110 


.02685 


2,325 


10.377 


21.129 


195 


195.697 


977.718 


1173.415 


.02740 


2,279 


10.597 


21.579 


196 


196.708 


977.012 


1173.720 


.02796 


2,234 


10.822 


22.036 


197 


197.719 


976.306 


1174.025 


.02853 


2,190 


11.051 


22.502 


198 


198.730 


975.600 


1174.330 


.02910 


2,147 


11.284 


22.976 


199 


199.741 


974.894 


1174.635 


.02967 


2,105 


11.521 


23.458 


200 


200.753 


974.187 


1174.940 


.03025 


2,064 


11.761 


23.948 


201 


201.765 


973.480 


1175.245 


.03083 


2,024 


12.006 


24.446 


202 


202.777 


972.773 


1175.550 


.03112 


1,985 


12.255 


24.953 


203 


203.789 


972.066 


1175.855 


.03201 


1,953 


12.508 


25.468 


204 


204.801 


971.359 


1176.160 


.03261 


1,916 


12.766 


25.992 


205 


205.813 


970.652 


1176.465 


.03323 


1,880 


13.028 


26.525 


206 


206.825 


969.945 


1176.770 


.03386 


1,844 


13.295 


27.067 


207 


207.837 


969.238 


1177.075 


.03450 


1,809 


13.568 


27.619 


208 


208.849 


968.531 


1177.380 


.03516 


1,775 


13.843 


28.180 


209 


209.861 


967.824 


1177.685 


.03584 


1,741 


14.122 


28.751 


210 


210.874 


967.116 


1177.990 


.03654 


1,708 


14.406 


29.332 


211 


211.887 


966.408 


1178.295 


.03725 


1,676 


14.700 


29.9218 


212 


212.900 


965.700 


1178.600 


.03797 


1,644 



INDEX. 



PAGE 

A 

Absolute information from diagram, - 79 
" pressure, ----- 21 

Action of steam in cylinder, theory of - 137 

" " " '' jacketed cylinders, - 141 

Actual curves, ------ 1C5 

Adiabatic curve, - - • - 105 

Adjuster for indicator cord, - - 31-72 
Admission line, ------ 92 

" late, 150 

" correctness of - - - 148 
•' " method of determining 

the correctness of, 149-151 
Amsler polar planimeter, - - - - 19S 
" meau effective 

pressure from, 198 
Application of indicator, - - - - 35 
Areas and circumferences of circles, 289 

Areas of large circles, finding 294 

Atmospheric line, - 75-91 
" " tracing, - - - 75 
Averager for measuring diagrams, - - 185 
Available power, 221 

B 

Back pressure, 219 

" cause of excessive, - - 219 

" in condensing and non- 

condensing engines, 220-277 
" loss from, - - - - 219 

total ----- 22 
" " line, - 22-94 

Blanks, example of printed, 78 

Boiler pressure, - 21 

Boilers, testing, ------ 277 

c 

Calculating water consumption by con- 
stant, 165 

Care and use of indicator, 68 

Carrying pulleys, 71 

Calorimeter tests, manner of making, - 248 

" rule for computing, - 251 



PAGE 

Calorimeters, different kinds, - - - 244 

Calorimeter, description of barrel, - 248 

" Trof. Carpenter's, - - 255 

Clearance, 22-23-S7 

estimating, ... 88 

" percent. 23 

" the effect of 219 

line, 87 

" locating, - 83 
Close agreement of the actual with the 

isothermal in jacketed cylinders, 143 

Coffin averager, 185 

" " construction of, - - 186 
" finding the meau effect- 
ive pressure with - 1S8 
" " principle of operation 

of the - - - 190-197 

Compression, ..--.. 22 

and clearance, - - . 219 

" curve, 95 

Comparison of diagrams from throttling 

and cut-off engines, - - - 201 
Comparison of results between large and 

small clearance, ... - 227 
Condensing engine diagrams, - 266-267 
Condensing and non-condensing dia- 
grams compared, - _ - . 227 
Condensation in cylinders, - - - 138 
" loss from - - - ' - 142 
Condenser, effect of adding - - - 214 
" pressure in - 214 
Condensation in uujacketed cylinders, - 139 

Cock, three way 30 

" section of three way 31 

Cord, indicator, - - - - - 72 

" adjuster ------ 31 

" stretching of the 72 

Computing horse power, - 112 
Computing steam accounted for by the 

indicator, different methods of 152-157 
Combining diagrams, metho.l of - 229-233 
from compound 

engines, - - 22S 



304 



Index \ 



PAGE 

Compound condensing- engines, dia- 
grams from, .... 261-268 
Curves, theoretical or isothermal - * - 97 
" agreement of actual and theo- 
retical expansion, ... 106 
Cut-off, the point of - - - - 93-212 
" locating the point of - - 108-m 
" the best point to - 214 



I> 

Data necessary, ------ 

" how to preserve - - - - 

Description of indicator, - - - - 

Device, indicator testing, - - - - 

Diagrams, indicator - - - - - 

'' the information to be derived 

from - 
from Marsh steam pump, 
" combining, - 

Diagram, essential features of a well- 
formed - 
" lines and points of the - 

Diagrams, to take simultanously - 
the outline of - 
engine underloaded 
not desirable - 
" reading the .... 

Diagram representing the economy of 

high pressure - 711 

Diagram showing the most favorable 

point of cut-off - 216 
Diagram from a steam jacketed cylin- 
der, 143 

Diagrams from both ends of a cyliuder, 85 
Diagram, good features of a - - - 80 
Diagrams., measuring a large number of 185 
Diagram, mmes of the lines of the 91-95 

Diagrams, study of 83 

11 method of taking 75 

from pumps, - - - 272-273 

Diagram averager - "185 

Diagrams from various engines, - 258-267 

Diagrams to show the effect between 

large and small clearance, - 219226 
Diagrams from steam cylinder and 



77 
77 
16 

175 
16 

-9-82 
274 
22S 

84 
91 
63 
83 
117 
123 
146 



ammonia compressor, 
Diagrams from gas engines, 

" from oil engines, 

" miscellaneous, 

Directions for indicating, 
Driving gear for indicator, 
Drum motion, testing accuracy of 
Drum stop motion, - 
Drum spring, .... 



239-240 

- 241 

- 242 
258-267 

- 75 
" 54 

- 52 
Ci-62 

- 74 



E 

Economy in the use of steam - 
" of expansion, 

" heating feed water, 
" high pressure, 
steam engine - 
Engines, testing .... 

" compound - 
" comparison of diagrams from 



- 282 
123-125-208 



209 

275 
282 
267 



throttling and cut-off 
Essential features of diagrams, 
Exhaust-closure, - 

Exhaust-closure, early and late, 
Exhaust, heat lost at - - 

Exhaust-line, - 
Exhaust-valve, leaky 
Expansion of steam, 

line or curve, - 
ratio of 
" initial - - - 

!t curve, peculiarities of 

line, and leaky valves, 
curve, agreement of actual 

and theoretical - 143-145 

curve, geometrical method 
of finding points in the - 101 
Experiments to determine the most 
favorable point of cut-off, 



202-207 

- 84 

- 94 

- 2iq 

- 210 

- 93 

- 148 

- 119 

- 93 

- 130 

22 

- 83 

- 147 



Feed-water, economy of heating 
Feed-water accounted for by the indi- 
cator, ----- 
Foot pound, .-.-.. 
Friciion, effects of 

" of indicator piston 

" " " how to de- 

termine - - - - 



215 



284 

152 
112 
179 
181 

182 



Gases, Mariotte law concerning 
Gas engines, diagrams from 
Gauge or boiler pressure, 
Guide or carrying pulleys, 
Guide pulleys, disadvantages of 
Gas and oil engine diagrams - 

H 



- 9' 
240-24] 



7i 
234 



Heat lost, 214 

" available ------ 210 

" latent ------ 20 

" lost at exhaust ----- 210 

" sensible - - - - - 20 

" the unit of 20 



Index. 



305 



PAGE 

Heat units 20 

High pressure, economy of 209 
High speed diagram compared with 

moderate speed, ... 267-268 

High speed engines, manner of using 

the cord ou 51 

Holes in cyliuder, position for indi- 
cator, 3 6 "37 

Hooking the cords, 5 1 

Horse power, elements of - - - 112 

" " finding the - - 112 
" " for one pound mean 

effective pressure, - - 113 

«« " indicated - - - 21 

"net 21 

" " factors for - - - 113 

" " byordinates ... 114 

Hyperbolic logarithms, - - - - 128 

" curve ..... 97 

'•' logarithms, table of 129 



Indicator, brief history of the 

Watts' original - 

14 " " construction of 

" McXaught .... 

" " description of 

" p^rts of 

" size of piston of 

purpose of the ... 

" care required in the use of - 

" Tabor .... 

" construction of parts of - 

" oiling the - 

" scales - - - - 

springs .... 

" " to use - 

'' appliances, cuts of - 

" electrical appliance 

,: testing devise, 



11 
11 
11 
12 

- 13 

- 14 

- 14 

- 16 

- 68 
24-25 
24-30 

68-183 

73-87 

32-33-34 

- 73 
44-53 

- 65 

- 175 
construction of 176 
manner of using 176 
information de- 
rived from - 180 

- 54 
parts of - 55-57 

" " directions for 

using - 58-60 
cord ...... 72 

" adjuster 31 

driving gear - 54 

how to attach the 75 

piston, the effects of momen- 
tum of 181 



reducing gear, 



PAGE 

Indicators, using one cr two - - 30-77 
Indicator diagrams, the production of 17-86 
" " explanation of 17-18-19 

" cylinder, warming up - - 75 

" card, proportionate length of 38 

" diagrams from various engines 257 

" piston, effects of a tightly 

fitting 182 

Initial expansion, 95 

Initial pressure, .... 92-213 

Isothermal curve, 97 

" " locating points on the 98 

44 44 geometrical method for 

constructing the 101 



Jacketing, cylinder, 



143 



I, 



patent heat, - - - 20 

Lazy tongs, ... 39-40 

" " proportion of - - 40-41-42 

Leakage - - - - - 79 

Leaky Valves, detecting by the indicator 106 
Length of diagrams, - - - 38 

Levers, reducing - 46-49 

Locating clearance line on diagram, 88 
" point of cut-off - - 108-111 

Long indicator pipes, - - - 37 

M 

Management and care of indicator, - 68 
Mariotte law of gases, - - 97 

Manner of taking diagrams, - - 75 

Marsh steam pump diagrams, - - 274 

Mean effective pressure, - - 22-95 

14 " " computing - 117 

44 44 " measuring by 

ordinates the 114 
Mean effective pressure, horse power 

for one pound, - - - 113 

Mean pressure of expanding steam, the 

rule for finding the - - 130-131 

Measuring diagrams, - - - 114 

Memoranda of diagrams, making - 77 

Method of indicating a steam engine - 75 

" computing horse power, 113-114 

Moisture in steam, - 244 

Motion, Watts' parallel - - 14 

" straight line - - 15 

" drum - 16-70 

Movement of pencil, - - - 16 



306 



Index. 



© 

Oil engines, operation of - .. - - 243 
Oil engine diagrams, - - - 242 
Oiling the indicator, - - 6S-1S3 
Ordinates, horse power by - - 114 
" different methods of measur- 
ing the - - 11&-117 



Paper-drum, - 

Pautagraph - 

" adjusting the - 

Paral'eV motion, Watts 
Parallel or straight line motion, - 
Pencil, adjusting the 
Pencil movement, proportioning of 
Pendulum reducing gear, - -^ 

Piping for indicators, 
Planimeters, 

Amsler polar 
Planimeter. measuring mean tffecti 

pr-ssure by the 
Point of cut-off, - 

" " exhaust, ... 
Pressure, ab-olute - 
" back - 

boiler - - . - 

" initial - 

*' mean effective 

" of expanding steam 

of expanding steam, rule 1 
finding the 
" terminal - 

" total back 
" for indicator springs 

Priming, extent of - 

Printed blanks. 
Pulleys, carrying - 
Pump diagrams, . - 



- 16 


44-45 


- 45 


- 14 


- 15 


69-70 


35-36 


47-40 


- 30 


- 1S4 


- 1 98 


- 184 


93-213 


- 93 


21-22 


- 219 


21 


21 


22-95 


- 123 


130-131 


22 



272-273 



R 



Ratio of expansion, 
Reducing levers, - "--■•• - • 

Reducing gears, different kinds of 5 

Re-evaporation, - - - - 

Resistance to motion of th - piston of a 

steam engine. - 

Rule for finding the mean pressure of 

expanding steam, :- - 13' 



Safe pressure for indicator sprin< 
Satuiated steam, 



2V9 



Scales, indicator - 
Sensib'e heat, ... 

Serrated lines of the diagram, 
Specific heat, - 

Springs, how marked, 
Spring to use, proper 
Springfield gas engine diagrams, 
Steam, dry .... 

" expansion of 

" li le 

" exhau ted per hour, 

" line, straight 

" per horse power per hour 

*' jacketed cylinders ; diagrams 
from - - - 

" pressure of expanding 

" pipe, large and small, 

pressure, working with hi^h 
and low, - - 

" properties of saturated 

'" saved in clearance, 

" superheated, 

" or water consumption, 

'' admission of 

" connections for indicators, 

" i:>. cylinders, (actio 1 of) - 

" accounted for by the indicator, 

M valve, leaky 



PAGE 
- 73 



21 
II 9 
92 



143 
123 

79 

2n8 

2 )5 
iij 

21 
2? 

84 

3' 

i;7 



Tabor indicator, - 24-25 

" " with reducing motion 

and parts, - . 5^-57 

'• " with electrical attach- 

ment - - -65 

" " with comb. ned pistons, 2 ,-■> 

Table of hyperbolic logarithms - - iz- 

" showing the theoretical economy 

of using steam expansivelv, - T32 

" of constants for finding the average 
pressure with any pressure of 
steam, - - - - - 134 

" of average pressure of steam in the 
cylinder with different rates of 
expansion, - - - - 135 

" quantity of steam accounted for by 

the indicator, - - 170- 171 

" sh uving saving < ffected by the use 

of feed-water heaters, - - -2S6 

" aieas and circumferences of circles 2S9 

properties of saturated steam, - 295 

properties rf water, - - 299 

Temnieai terms - 20-21-22-23 

Terminal pressure, - 55-147-275 



Index. 



307 



PAGE 

- 147 

- I4" 7 
" 277 
. 277 
■ 279 

02 



Terminal pressure, cause of high 
theoretical - 
Tests, different methods of making 

" what should be noted in making, 
Testing engines and boilers, 
Theoretical curve, object of drawing the 
" points from which to 

draw the - 98 

" reasons for establish- 
ing the - - 103 
Theoretical diagram, - - - 120 
economy of expansion, 126-1,13 
Three-way cock, - - - 30 

u 

Underloaded engines, - - 116-212 

Unit of heat, - - - .20 

'• work, - - - 20 

Uses to which the indicator may be 

applied, - jo 



Vacuum -line, establishing 
Valves, adjusting . 

" detecting leaky 
Valve lap, - 

" lead, ---■«. 

" gear, incorrect, 

w 

Watts' original indicator, - 

" parallel motion, 
Water consumption, making allowance 
for - . - - 

" per horse power per hour 
Wiredrawing - 

Work and heat - 

" in the two ends of the cylinder 

" the unit of - 



Zero line, 



164 
152 
23 
210 

83 
20 



ADVERTISEMENTS. 



The Improved Tabor Steam Engine Indicator 

With Outside Spring. 




With Houglitaling Reducing motion. 

Coffin Averagers, Amsler Planimeters, Pantographs, Lazy Tongs, Ashcroft 
Reducing Wheels, Three Way Cocks, Carrying Pulleys, Etc. 

•v warded Cirand F»rize at World's Fair, St. Louis, 1004. 

THE ASHCROFT MANUFACTURING CO., 

SOLE MANUFACTURERS 

85-87-89 LIBERTY STREET, 22-24-26 S. CANAL STREET, 

NEW YORK CHICAGO. 



ED SO IN 

Pressure Recording and Alarm Gauge 



For 

Steam, 

Air, 

Gas, 

Water. 




Ammonia 



or 



any 

Fluid 

Pressure, 



STYLE No. 1. 
Awarded Grand Prize at World's Fair, St. Louis, 1904. 

THE ASHCHOFT MANUFACTURING CO., 

SOLE MANUFACTURERS. 



85-87-89 LIBERTY ST., 
NEW YORK. 



22-24-26 8. CANAL ST., 
CHICAGO. 



Consolidated 
Nickel Seated 
Pop Safety Valve. 



Water 
Relief 
Valves. 




Cylinder 

Relief 

Valves. 



Awarded Gold Medal at World's Fair, St. Louis, 1904. 

The Consolidated Safety Valve Co., 

SOLE MANUFACTURERS. 

85-87-89 Liberty St., 22-24-26 S. Canal St., 

New York. Chicago. 



The Metropolitan Automatic Injector 



MODEL "BJ.' 




Especially adapted for Hoisting Engines, and for 

service where an Injector operated entirely 

by one handle is required. 

H-D EJECTORS, . . . . . 
H-D WATER HEATERS, Etc. 

Awarded Gold Medal at World's Fair, St. Louis, 1904. 

THE HAYDEN & DERBY MFG. CO., 

SOLE MANUFACTURERS. 

85-87-89 Liberty St., 22-24-26 S. Canal St., 

New York. Chicago. 



THE HANCOCK INSPIRATOR 



STATIONARY TYPE 




For Stationary and Portable Boilers. 

BEWARE OF IMITATIONS, and for your own protection see that the 
Inspirator is marked "The Hancock Inspirator Co." 

HANCOCK EJECTORS, HANCOCK COMPOSITE TYPE INSPIRATORS, &o. 

Awarded Gold Medal at World's Fair, St. Louis, 1904. 

THE HANCOCK INSPIRATOR CO., 

SOLE MANUFACTURERS. 
85-87-89 Liberty St., 22-24-26 S. Canal St., 

New York. Chicago. 



The Hancock Valve 

MADE IN 

GLOBE, ANGLE, SIXTY DEGREE and CROSS. 




For high pressure steam, 

For superheated steam, 

For hot water, 

For Blow-off, 

For severe conditions gen 
erally. 



HANCOCK CHECK VALVES 

HANCOCK BLOW-OFF VALVES, &c. 

Awarded Gold Medal at World's Fair, St. Louis, 1904. 

THE HANCOCK INSPIRATOR CO,, 

SOLE MANUFACTURERS. 

85-87-89 Liberty St., 22-24-26 S. Canal St., 
New York. Chicago. 



Manning, 
Maxwell & 

MOOre, Incorporated, 

Railway and Machinists' 
Tools and Supplies. 



85-87-89 Liberty Street, New York. 



Branch Offices: 

22-24-26 S. Canal Street, Chicago, III. 
721 Arch Street, Philadelphia, Pa. 
128 Oliver Street, Boston, Mass. 
Park Building, Pittsburg, Pa. 
Williamson Building, Cleveland, O. 
Frisco Building, St. Louis, Mo. 
Woodward Building, Birmingham, Ala. 
Kirk Building, Syracuse, N. Y. 



The SHAW ELECTRIC TRAVELING CRANE. 




Sixty ton Electric Traveling Crane, Subway Station, Interborough Rapid 
Transit Company, New York City. 

For tlie Machine Shop, the Power 
House, the Foundry, the Steam Plant. 

Awarded Grand Prize at the World's Fair, St. Louis, 1904. 

THE SHAW ELECTRIC CRANE CO., 

SOLE MANUFACTURERS, 



85-87-89 LIBERTY STREET, 



NEW YORK 



BRANCH OFFICES: 

22-24-26 S. Canal St., Chicago, III. Williamson Building, Cleveland, O. 

721 Arch St., Philadelphia, Pa. Frisco Building, St. Louis, Mo. 

128 Oliver St., Boston, Mass. Woodward Bldg., Birmingham, Ala. 

Park Building, Pittsburg, Pa. Kirk Building, Syracuse, N. Y. 



SE? 26 1906 



HSE. ARY 0F CONGRESS 





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